## 4. Genomics and Molecular Biology

Understanding the molecular biology of *N. locustae* is fundamental in determining its biology and molecular interactions with the host and improving applications in its use for pest control. A complete genomic sequence of *N. locustae* has recently been revealed by Chen et al. [45], which is a major achievement. Sequencing of its genome yielded 3,170,203 nucleotides, encoding for 1857 predicted genes, of which 1755 are single-exon genes, and 102 are multiple exon genes. A total of 17 scaffolds, ranging from 88.763 to 388.82 kb, were identified and assigned to 17 chromosomes. Genomic and protein sequences from *N. locustae* and several other single-celled organisms were used to study evolutionary relationships in genetic synteny and collinearity using the MCScanX method. Results showed that within the microsporidia, most genes exhibit good collinearity [45].

In addition to genomic sequencing, Chen et al. [45] performed an analysis of locust midgut transcripts versus locust fat body transcripts from *N. locustae* infected locusts. They found that the abundant expression of locust antimicrobial peptides and other defense genes, such as peroxiredoxin and amine oxidase in the midgut, may explain the lower number of microsporidian spores in the midgut of the host. In the fat body, however, the large number of *N. locustae* spores present may be related to the fact that several locust phenol oxidases and peroxisome proliferator-activated receptors have been inhibited to allow it to escape the host immune response. This revealed the interactions of *N. locustae* and the host at the transcript molecular level, in particular why *N. locustae* can reproduce massively in the locust fat body and not in the gut.

Identification of the genes and proteins of the polar tube is certainly useful in understanding the interactions between *N. locustae* and its hosts at the molecular level. Two polar tube protein genes, PTP1 and PTP2, have been identified, and it has been suggested that PTP1 plays a key role in interactions with the host cell surface [46]. Two other orthologous polar tube proteins, named AlPTP2b and AlPTP2c, exhibit elastomeric characteristics. The AlPTP2b and AlPTP2c genes encode for proteins of 568 and 599 amino acids with deduced molecular weights of 55,399 and 56,664 Da, respectively. These proteins are highly conserved (84.2% identity), larger than the previously reported AlPTP2 (287 amino acids) [47].

Fast et al. [48] identified a gene for the TATA box binding protein (TBP) of *N. locustae*. The predicted amino acid sequence of the TBP gene consists of 259 amino acids. In the phylogenetic analysis of TBP, the authors emphasized that TBP from *N. locustae* is close to that of fungi and supported previous studies on the evolution of microsporidia with tubulins, HSP70, and the greater subunit of RNA polymerase II (RPB1) proteins [49–53]. However, in a study on the large subunit (LSU) rRNA, Peyretaillade et al. [54] proposed that the origin of microsporidia was not specifically linked to a particular group of eukaryotes. In general, there are only a few studies on proteins and genes of *N. locustae* [55], and even rarer studies on their functions, especially pathogen–host interactions at the molecular level.

## 5. Mass Production and Products

The production of *N. locustae* spores is done in vivo. The rearing of infected hosts is the main process for mass production (Figure 2). Grasshoppers *Melanoplus bivittatus* (Say, 1825) have been used as hosts in the United States. Henry et al. [10] pointed out that several factors influence production yield. Cage size and the number of individuals in each cage, light in the cage, and time of harvest, as well as factors such as grasshopper species and sex, are important. The general process is as follows: grasshopper nymphs are reared to the 4th–5th instars, inoculated with *N. locustae* spore suspension, and then reared until they die. The cadavers are collected and crushed, screened, and centrifuged to obtain a high concentration of spores, which are stored between –10 and –20 °C. In the United States, after several improvements in mass production techniques, a yield of 1 × 10⁹ to 3 × 10⁹ spores per grasshopper has been achieved. However, the use of *Melanoplus differentialis* (Thomas, 1865) as a host resulted in up to 7.1 × 10⁹ spores per
individual [56]. The time of harvest is an important factor in influencing the spore yield;
the further away from the inoculation date, the more spores are obtained [17].

<figure><img src="image_131.png" /><figcaption>**Figure 2.** Mass producing process of *N. locustae* spores.</figcaption></figure>

In China, *L. migratoria manilensis* has been selected as a host to produce spores of *N. locustae*. In this species, there is no diapause, and individuals can be used year-round. Several factors influence the efficiency of mass production, including the inoculation concentration, the stage of development for inoculation, and the harvesting time [57]. A higher concentration of spores in the inoculation suspension resulted in rapid locust death, and a lower concentration increased the time to harvest and reduced the number of spores. The best inoculation concentration was found to be 1 × 10⁶ spores/mL, the stage for inoculation the fourth instar, and the harvest time about 30–40 days after inoculation. The average spores/individual yield was approximately 6 × 10⁹, the highest being about 9.9 × 10⁹. In China, several insectariums have been established for the mass production of *N. locustae* since the 1990s. Currently, the average spore yield per individual can reach 22 × 10⁹ to 34 × 10⁹. There are about 5–6 harvests per year, and the total yield can reach 2 × 10¹⁵ spores for each insectarium [17].

The products are usually formulated either as bran bait, aqueous suspension, or
water-based suspension. They are prepared from high concentrations of spores stored at
low temperature, diluted directly with water or mixed with wheat bran in an appropriate
ratio. In China, a new water-based suspension has been developed. The spores are
mixed with xanthan gum, sorbic acid, and other environmentally friendly additives. The
suspension is more stable and homogeneous and can be stored for about one year at
room temperature [58]. It is better adapted to the needs of users and should be widely
applied. To date, several commercial products have been registered such as Nolo Bait™,
Semaspore™, and Grasshopper Attack™ in the United States since the 1980s [12]. In China,
*Nosema locustae* products for locust control have been developed since the 1990s and are
currently distributed by Beijing JiaJing Biotechnology Ltd. (Beijing, China). They are based
on a highly pathogenic strain (AL2008L-04) that significantly improves product efficacy,
a high-yield production technology, and an aqueous suspension formulation that can be
stored at room temperature [59].
6. Application and Epizootics

The three main components whose interactions can lead to a reduction in locust and grasshopper populations and epizootics are *N. locustae*, its hosts, and its environments. *N. locustae* has been used to control *L. migratoria manilensis* since the 1990s. A field trial was conducted on Hainan Island, China, in areas close to rice fields [60]. The locust population consisted of first to third instars with pretreatment densities of 0.9, 1.5, and 2.2 individuals/m² in the three treatment plots and 0.6 in the control plot. The plots were treated at 50 × 10⁹, 99 × 10⁹, and 150 × 10⁹ spores/ha. At 25 days after treatment, the locust population density was reduced by 70.2%, 74.0%, and 78.9%, respectively, in the treated plots but increased by 58.1% in the control plot. The prevalence of *N. locustae* infection in survivors was 29.4%, 31.1%, and 31.8% at 30 days and 40.6%, 40%, and 35.7% at 40 days after treatment in the treated plots. The prevalence of infection persisted the following summer (one year) in the three treated plots, respectively, at 23.5%, 13%, and 9.1% levels.

In the United States, in Montana, studies indicated that the prevalence of *N. locustae* during the treatment season was variable, but mainly around 30%, with the highest being 50% when the spore application rate was 1.4 × 10¹⁰ in 1.12 kg of wheat bran/ha after three applications [10,61]. In Canada, in a grasshopper population consisting mainly of third instars of *Melanoplus sanguinipes*, *M. packardii* (Scudder, 1878), and *Camnula pellucida* (Scudder, 1862) treated with 2.5 × 10⁹ or 5.0 × 10⁹ spores in 1.68 kg wheat bran per ha, an infection rate of approximately 50% was observed 4–5 weeks after treatment [62]. Toward the end of the season, about 12 weeks after treatment, this rate was about 95–100%. Zhang et al. [63] reported the prevalence of *N. locustae* in the years following the application of spore-based baits to mixed grasshopper populations—consisting of *Oedaleus asiaticus* Bey-Bienko, 1941, *Myrmeleotettix palpalis* (Zubovski, 1900), *Angaracris rhodopa* Fischer von Waldheim, 1836, *A. barabensis* (Pallas, 1773) and *Dasyhippus barbipes* (Fischer von Waldheim, 1846)—in Inner Mongolia rangelands, a region where temperatures are below −10 °C in winter and 20 to 30°C in summer and rainfall is about 200 mm per year. In two areas treated in 1991 and 1992 with 7.5 × 10⁹ spores/1.5 kg wheat bran bait/ha, locust infection rates of *N. locustae* were 14.5% and 19.8% in the second year after treatment. In a third area treated in 1988 with *N. locustae* baits, the observed infection rates were 6.8% and 23% two and six years after treatment. Mortality rates of 60–80% in mixed grasshopper populations were achieved following applications of *N. locustae*, in Inner Mongolia rangeland, at a rate of 3 × 10¹⁰ spores/ha for two consecutive years [64]. *N. locustae* was even used in the highlands (3270–3350 m ASL) in Qinghai province of China, and the disease could still be transmitted and persisted for a long time among grasshoppers [65], up to 10 years with an infection rate exceeding 50% in some years [27]. In three locations in Canada in two consecutive years (1988–1989), Johnson and Dolinski [66] found that *N. locustae* persisted in grasshopper populations. They suggested that the activity of *N. locustae* was not inhibited despite severe weather conditions, hot in summer and very cold in winter, with air temperature down to −39 °C.

*N. locustae* was reportedly applied in a forest to control the yellow-spined bamboo locust (*Ceracris kiangsu*) [25]. In a 1.5 ha area of bamboo sprayed with 50 kg of *N. locustae* spore suspension at a concentration of 5 × 10⁷ spores/mL, mortality of *C. kiangsu* was 85% 15 days after treatment. *N. locustae* was also used in 2018 to control the yellow-spined bamboo locust in bamboo forest ecosystems in Phongsaly province, Lao [67]. Nymphs were in the third and fourth instars at a density of over 100 individuals/m². Treatment was carried out on May 13 at an application rate of 2 × 10⁷ spores/mL. After 17 days, many dead locusts were observed in the treated area, where the average density was less than 10 individuals/m², a reduction of more than 90% compared to the untreated control area. *N. locustae* spores were observed in all dead locusts that were collected from the treated plots and examined individually under a microscope in the laboratory. The average grade of infection was three out of five, corresponding to severe disease. In contrast, the infection rate of locusts collected from the control area was zero. In addition, 46% of surviving
locusts in treated plots were infected with *N. locustae*, and two and a half months after treatment, the density was very low, about 0–2 individuals/m². It was concluded that *N. locustae* could be an effective agent to control high densities of yellow-spined bamboo locusts in bamboo forests.

In Africa, Tounou et al. [68] conducted field trials to assess the effects of *N. locustae* and *Metarhizium anisopliae* against various grasshopper species: *Pyrgomorpha cognata* Krauss, 1877, *Acrotylus blondeli* Saussure, 1884 (both predominant species), and *Oedaleus senegalensis*. Both agents were mixed with wheat bran as bait with *M. anisopliae* alone, *N. locustae* + *M. anisopliae*, *N. locustae* spores alone, or *N. locustae* + sugar. The same treatments were carried out with *O. senegalensis* in the early stages of development and resulted in mortalities of 64–85%. The population density during the three weeks of monitoring decreased by 44.7 ± 6.9% in the *N. locustae* plot, 52.8 ± 8.4% in the *N. locustae* + sugar plot, 73.7 ± 5.5% in the *M. anisopliae* plot, and 89.1 ± 1.8% in the *N. locustae* + *M. anisopliae* plot. The prevalence of *N. locustae* in adult grasshoppers surviving at 28 days after application was 48.1 ± 2.3, 28.9 ± 4.8, and 27.4 ± 3.7% in the three treatments with *N. locustae*. The results suggest that these two biological control agents have the potential to control the early stages of grasshoppers in Africa. These conclusions differ from those of Lima et al. [69], who found no significant difference between treated and untreated plots and concluded that *N. locustae* could not be used to control *O. senegalensis* in the Cape Verde archipelago. However, they did not specify the developmental stage of the treated grasshoppers, and it is possible that efficacy was less on the fifth nymphal instar or on adults.

Long-term epizootics of *N. locustae* have been investigated in Argentina by Lange et al., who have shown that this pathogen can persist for many years after its introduction [30,70,71]. These authors, in their field survey, found that the prevalence of *N. locustae* ranged from 1.8 to 41% in 9 of 13 sites between 1995 and 2003. In 1990, in another field survey in an area treated 11 years earlier, Lange and Azzaro [71] observed infection rates of 2.9%, 3.5%, and 3.6% by *N. locustae* spores in three grasshopper species, *Dichroplus elongatus* Giglio-Tos, 1894, *D. maculipennis* (Blanchard, 1851), and *Scotussa lemniscata* (Stål, 1861). Lange et al. [30] examined grasshoppers collected from sites treated with *N. locustae* in Argentina in the late 1970s, early 1980s, and mid-1990s and found that the highest prevalence of *N. locustae* in grasshopper populations was about 50%.

## 7. Conclusions and Prospects

*N. locustae* is becoming increasingly biologically understood, as well as for its potential in L&G control. Recent studies have shown that it can be applied in different ways to achieve control objectives and plays a more important role than ever in locust and grasshopper management programs. It has a fairly broad host spectrum, and at least 144 orthopteran species are susceptible. However, it is very safe for non-orthopteran insects and other non-target animals [17,33]. It is transmitted orally and is therefore probably less sensitive to environmental factors than fungal-type agents. This is certainly the reason why good results have been recorded at a 3000–4000 m altitude on the Tibetan plateau in China and in high-temperature regions such as Hainan province in China or Lao and Vietnam. *N. locustae* has been demonstrated to be efficient in the control of L&G in rangelands, crop fields, and forest ecosystems. Its disease can persist for many years after application in L&G populations and can be part of their long-term management.

When L&G are at low density, a low dose of *N. locustae* will slowly kill them as a long-term control method. However, recent field trials have indicated that *N. locustae* can also be used at high locust densities, as has been demonstrated to control second and third instars of the yellow-spined bamboo locust. *N. locustae* also exhibits a synergistic effect when used in admixture with the fungus *Metarhizium* spp. and can potentially weaken the host immune response by reducing its defensins. The simultaneous use of *N. locustae* and *Metarhizium* spp. could be encouraged to control high-density locust outbreaks.

L&G mortality caused by *N. locustae* is dose-dependent; the higher the dose used, the higher the mortality. However, *N. locustae* spores are produced restrictively in vivo. The
mass rearing of locusts to produce spores is expensive; therefore, increasing the spore yield per locust or grasshopper is a bottleneck for mass production and large-scale application. Understanding the molecular mechanisms of *N. locustae* and its interactions with its host may be valuable to explore ways to mass-produce *N. locustae* spores in order to improve the traditional in vivo mass production method or to find an alternative, as well as to increase the effects on L&G. Genome sequencing and transcriptomic analysis of *N. locustae* genes and proteins have provided a valuable basis for future studies to improve the genetics of *N. locustae* and screen for high-virulence strains [72]. The development of new formulations and other technologies to maintain high spore vitality at room temperature will also be useful in promoting the wider application of *N. locustae*.

**Author Contributions:** L.Z. conceived the article and drafted the manuscript with substantial input from M.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work is supported by a grant from Shandong Academy of Agricultural Sciences, and a grant from the Ministry of Agriculture of China (15206030).

**Acknowledgments:** Authors would like to thank anonymous reviewers' comments and suggestions.

**Conflicts of Interest:** The authors declare no conflict of interest.

**Disclaimer:** Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the authors.

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Article

# Locusts and People: Integrating the Social Sciences in Sustainable Locust Management

Clara Therville<fnref n="1" />,*, John M. Anderies <fnref n="1" />,<fnref n="2" />, Michel Lecoq <fnref n="3" /> and Arianne Cease <fnref n="1" />,<fnref n="4" />

**Abstract:** Locust outbreaks have impacted agricultural societies for millennia, they persist today, and humans aim to manage them using preventative strategies. While locusts have been a focus for natural sciences for more than a century, social sciences remain largely underrepresented. Yet, organizational, economic, and cultural variables substantially impact these management strategies. The social sciences are one important means through which researchers and practitioners can better understand these issues. This paper examines the scope and purpose of different subfields of social science and explores how they can be applied to different issues faced by entomologists and practitioners to implement sustainable locust research and management. In particular, we discuss how environmental governance studies resonate with two major challenges faced by locust managers: implementing a preventative strategy over a large spatial scale and managing an intermittent outbreak dynamic characterized by periods of recession and absence of the threat. We contend that the social sciences can help facilitate locust management policies, actions and outcomes that are more legitimate, salient, robust, and effective.

**Keywords:** environmental governance; social variables; locusts; social sciences

**Citation:** Therville, C.; Anderies, J.M.; Lecoq, M.; Cease, A. Locusts and People: Integrating the Social Sciences in Sustainable Locust Management. *Agronomy* **2021**, *11*, 951. https://doi.org/10.3390/agronomy11050951

Academic Editor:
Nikolaos Papadopoulos

Received: 18 April 2021

Accepted: 7 May 2021

Published: 12 May 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

<figure><img src="image_132.png" /></figure>

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## 1. Locust Science Needs Social Sciences

It is evident to all researchers and practitioners concerned by locusts that these insects have always been of great concern to people socially, culturally, economically, and politically. Locusts are currently considered by the FAO as "one of the most destructive migratory pests in the world" (http://www.fao.org/locusts/en/, accessed on 10 May 2021): there are at least 20 different agriculturally important locust species affecting the economies of most continents, a large range of more or less developed countries, and the livelihoods of millions during outbreaks [1,2]. In addition to impacting vulnerable agricultural communities in the short term, a locust plague can have long-term consequences such as spurring migration to urban areas, decreased access to education for children, exacerbating tensions between pastoralists and farmers, and overexploitation of natural resources [3,4]. Control campaigns can cost many millions of dollars [5], and the chemical insecticides used can have serious side effects on human health and the environment [6,7]. Locusts are also an object of political power. For example, Peloquin (2013) demonstrated how the French colonial empire designed the management of the desert locust crisis in 1943 to be perceived as a transnational and constructive federation against a common enemy (locusts), but in ways that strengthened its authority during a geopolitical legitimacy crisis [8].

Throughout history, humans have predominantly considered locusts as a threat and have tried to protect themselves from them. Until about the last one hundred years, locusts were described as literally falling from the sky and anticipating invasions was impossible [9]. The urgency to find solutions to this agricultural challenge led governments

<footnote n="1">¹ School of Sustainability, Arizona State University, Tempe, AZ 85287, USA; m.anderies@asu.edu (J.M.A.); acease@asu.edu (A.C.)</footnote>

<footnote n="2">² School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85287, USA</footnote>

<footnote n="3">³ CIRAD, UMR CBGP, F-34398 Montpellier, France; mlecoq34@gmail.com</footnote>

<footnote n="4">⁴ School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA</footnote>

<footnote>* Correspondence: clara.therville@gmail.com; Tel.: +33-6-7959-9705</footnote>
to support scientific research, locust ecology in particular, to locate main breeding areas (outbreak areas) and develop more efficient survey and control methods [10]. It was the discovery by Uvarov of locust phase polyphenism [11,12] that directed field research towards locating outbreak areas from the 1930s, and thus provided a rationale for preventive strategies around the world [10]. This discovery induced a paradigm shift from old reactive approaches focusing on crop protection in a context of complete uncertainty to anticipative preventive strategies and risk management systems [13–15]. Many entomologists around the world thus devoted their careers to exploring the best potential biological and ecological solutions to deal with the locust problem [10]. Since then, tremendous scientific work, especially in the natural sciences, as well as technological advances for example in communication, remote sensing imagery and climatic and weather data collection were developed to manage locusts [13,14]. The current preventive strategy relies on the surveillance of areas prone to producing gregarious populations, which ultimately help people make decisions for control according to locust densities and location of infestations, using either chemical, biological or ecological control [13,14]. However, this strategy remains questioned, as illustrated by the debate that followed the 2003–2005 desert locust invasion [16,17]. Locust outbreaks continue to arise and some authors wonder if sustainable locust management is possible [18].

This observation has led some scientists and practitioners to insist on the social and organizational variables that may impact locust management [19]. Research has described this impact on our capacity to understand and manage locusts since the end of the 19th century for different locust species in different part of the world (see, e.g., [10,20]). These studies point out the social constraints to maintaining an efficient preventive strategy through time and through large spatial scales. Recent reviews highlight a common and significant constraint for sustainable locust management: the reduction of resources during recession times [14]. As one of the most well-known species, the case of the desert locust provides old testimonies of this challenge. Roy, an historical expert in the fight against locust invasions in West Africa, looked back at the conditions that made the great invasion of 1987–1989 possible through the degradation of an existing preventive control strategy [21]. He highlights the impact of the loss of knowledge during recession times, induced by the dismissal or retirement of field staff and researchers. Past and current outbreaks of the desert locust have also been explained by armed conflicts and insecurity that have led some countries to lack capacity to sustain expertise, monitoring, and control [22,23]. In 2005, Lecoq insisted on the need for stronger risk-management systems, and put an emphasis on governance, funding, flexibility and a better understanding of the role of locust-control stakeholders [19]. Fifteen years later, the identified highest priorities to face desert locust outbreaks sounds familiar [22]: “(a) to ensure that the political and socio-economic conditions are in place so that vulnerable human populations can adapt to new large-scale threats and (b) to maintain a culture of long-term risk assessment with constant necessary means”.

The social sciences are one means through which researchers and practitioners could come to understand the social variables that impact locust management. However, paradoxically, while locust management is seriously constrained by organizational, economic, and coordination issues [14], social sciences are underused in locust research. There are numerous recent studies on locust biology and on the use of remote sensing technologies to improve locust management systems (reviewed in Cullen et al. 2017) [24]. We do not question the fact that further research is needed on genetics, ecology, population dynamics, or remote sensing to improve our knowledge of locusts and management strategies, especially under a changing climate. However, more than fifteen years after the call to switch locust management “from ecology to anthropology” [19], social sciences are still overlooked in locust studies. That being said, counter-examples can be found. For instance, economics has already provided useful arguments to defend preventive strategies for locusts. In the case of the Australian plague locust [25], the benefit–cost ratio for all the control campaigns of the 2010–2011 plague is estimated at 19:1, indicating that every dollar invested in locust control generates $19 in avoided losses.
This call towards social sciences also meets other calls towards the reframing of risk management, crop pest management, insect science, and locust management in particular, using social-ecological, sustainability, and transdisciplinary approaches [26–28]. A social-ecological approach is a way to emphasize the interlinked social and ecological dynamics and the cross-scale and cross-level social-ecological complexity involved in managing the environment [29,30]. For example, Cease et al. [31] described the locust-grassland-human system as a coupled human and natural system, implying complex feedback that connect geographically distinct people and places across time (ecological connections with locust migration or socio-economic connections through markets). Considering locusts as a “wicked” problem [32] also induces new ways of doing science, capable of dealing with problems characterized by high stakes, uncertainties, values in dispute, and urgent decisions [33]. In such a renewed frame, research not only has to be scientifically robust, but should also be more involved in the resolution of societal problems and promote the participation of civil society. This requirement justifies an extension of the peer community involved in the resolution of environmental problems, including social scientists, and the mobilization of both interdisciplinarity (within academia but across disciplinary boundaries) and transdisciplinarity—also referred to as cross-sectoral (across the professional boundaries between researchers and practitioners, including managers and agriculturists in this case) [34].

In response to calls to make social sciences mainstream in locust research and management, this paper provides a succinct guide and overview of the social sciences for present and future locust managers, for natural scientists leading or participating in multi-stakeholder processes and interested in strengthening the role of social sciences, and for social scientists interested in locust research. We consider that the failure of social science to be mainstreamed stems in part from a lack of clearly articulated objectives and values associated with the social sciences. This article firstly identifies the distinct contributions that different fields of the social sciences can make to understanding and improving locust management. Then, we detail the main social challenges faced in locust management and how different areas of social science can shed light on them. In particular, we mention other examples of risk studies (e.g., shocks such as earthquakes or floods), institutional approaches used in these cases, and advancements surrounding the resilience of complex social-ecological systems. We conclude with a discussion of several key considerations for better engaging with the social sciences to improve locust management.

## 2. What Are the Social Sciences?

The social sciences are a set of tools and ideas that focus on how humans make decisions, create and maintain social relations, and how these individual processes lead to macro-level patterns of organization, such as interest groups, cultures, or nation states. Locust management involves decisions of individual farmers, managers, and policy actors, as well as the relationships among these actors (e.g., information exchange, coordination of activities). These decisions and relationships lead to macrolevel patterns (e.g., organizations to manage locust outbreaks across the spatio-temporal expanse of locust outbreaks). Thus, social science is a useful tool to understand the human and social dimensions of environmental issues in general [35], and of locust management in particular. Yet their absence is commonly reported in environmental studies, either dealing with global environmental change research [36], biodiversity conservation [35], or pest management [26,37]. This can be observed in the locust community through the limited number of social scientists participating in locust symposia and in locust review papers [24]. The barriers impacting the integration of social sciences and natural sciences has been particularly explored in the field of conservation sciences [38,39]. These papers highlight how, among many natural scientists and practitioners, there remains a lack of awareness about the social sciences. This knowledge void interferes with the ability to engage with the social sciences in a constructive manner that can inform management practices [35,40]. The multiple challenges that are known to interfere with the integration can be conceptual (e.g.,
confusion over the role of social sciences, different expectations, and/or disagreements on frameworks, definitions or concepts) or structural (e.g., lack of social scientists, compartmentalized organization, and/or lack of funding or opportunities for interdisciplinary collaborations) [38,41]. Another common challenge is the instrumentalization of social scientists to better package or market ecological knowledge [38], that devalues the knowledge they produce. Conversely, the critical approach developed by some social scientists on the "politics of nature", highlighting the role of ecology in power relations and injustices [39], has led to misunderstandings and even to a mistrust between social and natural scientists. Resolving these challenges requires a mutual respect and a basic understanding of respective approaches: both social and natural scientists should be able to identify the different disciplines embedded in the other realm, and be aware of the philosophical principles and theoretical assumptions of each of these disciplines [42]. On the other hand, each scientist should be able to make their discipline more digestible for scientists originating from other disciplines, through a more straightforward use of language, direct communication and accessibility of research findings [39].

Without going into detail—see Moon and Blackman [42] or Bennett et al. [35] for a more complete understanding of the social sciences—we provide here some elements of social science ideas and theory relevant to locust management. Social sciences are used to study five broad categories of the social realm: (i) social phenomena (e.g., markets, governance, politics, culture, demographics), (ii) social practices and processes (e.g., social organization, decision-making, knowledge exchange, collaboration), (iii) social attributes (e.g., social capital, trust, memory), (iv) actors, roles, and positions (e.g., bridging organizations, leadership), or (v) individual attributes (e.g., values, beliefs, knowledge, motivations, preferences, behaviors) [35,43]. They include disciplines such as sociology, anthropology, political science, geography, economics, history, psychology, and other more applied social sciences such as education, development, or communication science. Each discipline has specific topical strengths (e.g., governance for political science, social interactions and social facts for sociology, communication science to inform communication strategies during a crisis) and relies on established and specific bodies of social theories. Specific disciplines of the social sciences have included environmental concerns, such as environmental psychology or environmental economics. To tackle complex social-ecological problems, multiple interdisciplinary fields have emerged as well such as the resilience of social-ecological systems [29], environmental social science [44], political ecology [45] or environmental humanities [46]. All of them highlight the interconnectedness between the biophysical and the social and are supposed to facilitate the engagement between natural and social scientists.

Social sciences can be conducted on issues at different scales, from individual to local to global. The individual scale might be adopted to study perceptions, attitudes, or behaviors. For example, what are the preferences of farmers regarding the use of insecticides [47]? At the global scale, scientists might study governance models and the impact of decentralization in locust control [48]. The applications of social sciences vary from predicting, understanding, emancipating, or deconstructing the issue of interest [42]. They can focus on understanding social phenomena, testing or developing theories, and/or giving critical insights on a situation to overcome injustices. More applied social science fields such as communication science can help to think about the role played by information and communication technologies to promote coordination and appropriate responses in the face of extreme events [49], e.g., locust plagues. Methodology can be qualitative (e.g., interviews, focus groups, discourse analysis), quantitative (e.g., closed-ended questionnaires, cost-benefit analysis), participatory (e.g., participatory action research, photovoice), and/or forward-thinking (e.g., scenario planning, economic modeling) [35]. Alongside this "social science" panel, the arts and humanities, which designate knowledge fields related to culture in general (including history, philosophy, cultural and science studies or literature) should also be mentioned as an important complement to both social sciences and natural sciences. They question our values, our representations, our responsibilities [46], and provide sensitive means to address these fundamental issues.
### 3. An Overview of Existing Social Science Contributions to Locust Management

Although poorly represented, social sciences are not completely absent from the locust research and management world and some contributions can be found. They can be differentiated depending on their disciplinary approach and on their applications, from more analytical to more applied (Figure 1). Figure 1 is an attempt to summarize these distinctions and highlight some of the major contributions of the social sciences applied to locust management. The proposed categories are not necessarily exclusive from one another, nor as clear as they appear in Figure 1 since this should rather be seen as a continuum.

<figure><img src="image_133.png" /><figcaption>**Figure 1.** A framework to summarize some of the main types of studies in locust science that include social sciences, depending on their disciplinary approach and on their applications, from more analytical to more applied. In additional references, some papers may not focus on locusts but are representative of a given approach, e.g., [50].</figcaption></figure>

Diverse disciplinary approaches can be found in the social science literature on locusts: contributions can be embedded in one subdiscipline of the social sciences, such as sociology [9] or economics [25]; they can emerge from social science fields that are specifically interested in environmental issues, such as environmental history [10] or political ecology [51]; finally, they can come from interdisciplinary and transdisciplinary groups of authors who are willing to address the social variables impacting locust management [31,48]. Such papers may involve both entomologists/natural scientists alongside social scientists (interdisciplinary approach) and practitioners (transdisciplinary approach) who sometimes have a strong interest in social sciences and can even be double-hatted at the same time, being a practitioner or entomologist and trained as a social scientist. These contributions also reflect diverse possible applications: while some of them aim to describe and understand social phenomenon from an analytical point of view [9], others are clearly oriented towards action: they urge some changes in the ways we are thinking, managing and governing locusts outbreaks [19,48], are assessing the economic feasibility of current management strategies [25] or are exploring the possibility to use renewed instruments in locust management, such as payments for ecosystem services [52] or compensation funds [47].

Along this framework (Figure 1), four main categories of studies can be identified. First, studies embedded in an analytical approach and rooted in classical fields of the social sciences such as sociology or history can be found in the lower left corner. Interestingly, history is a particularly well represented discipline with contributions focusing on the desert locust [8], the South American locust [10], the Australian plague locust [53] and the
Moroccan locust [20]. These studies can focus on a specific event in history, such as the 1943 conference convened to discuss ongoing locust plagues in Northwestern Africa [8], or retrace a longer history of structuration of locust management of over 50 years [10,20]. Lessons learned include perspectives on historical distributions of locust invasions, explanations regarding the ineffectiveness of the measures taken, including a lack of transboundary coordination [20], or the strong interactions between political power and scientific research, leading entomologists to be recognized as public scientists [10]. By learning lessons from the past, environmental history offers enormous potential to inform contemporary locust management. According to Gomes et al. [20], histories can help to change the world and "Neglecting the history of locusts [...] is a step towards forgetting the presence of the species...,", which is a key concern in locust management, as we will discuss later.

Second, studies located in the upper left corner of the figure were written by inter-disciplinary and transdisciplinary groups of authors, even if they were still embedded in a particular analytical perspective. This includes what we have called social-ecological systems or “SES”approaches, which draw on theory from ecology, economics, and political science to focus on understanding the complex dynamics generated by multi-level interactions (interactions on multiple temporal and spatial scales linked across different levels of social organization) between inter-related social and ecological systems. These studies have been strongly influenced by systems theory and resilience studies and used concepts such as coupled human and natural systems, telecoupling, scales and scale mismatch, feedback loops or complex adaptive systems [30,54,55] to discuss the complex, and sometimes long-distance social-ecological interactions within the locust system. Ecologists can be pushed towards such an approach when studying the interactions between locusts and their environment, which thus includes the impact of human practices (crop farming, grazing) on the surrounding environment. For example, Cease et al. [31], Le Gall et al. [56], Word et al. [57] and others before them [58,59], demonstrated there can be a substantial impact of overgrazing or the type of crops and soil management regime on locust dynamics. This opens a space for discussion to include land management practices as a way to manage locusts, and thus to include farmers and their social environment (e.g., markets, policies) as key players. Within this family of systems studies, Gay et al. [60,61] focus on the ability of the current preventive system to manage desert locust plagues. Using multi-agent systems that include both human (e.g., field teams, national control units, funding institutions) and non-human agents (e.g., locusts), they explore the role of funding institutions’ awareness, budget cyclicity, and the lack of access to some areas due to insecurity. This last topic has also been recently explored by Showler and Lecoq [23] who demonstrated the various effects of armed conflicts in the case of the desert locust over the last 35 years. Lastly, some studies develop a particular interest for collective action and governance in general. For example, Toleubayev et al. [62] focuses on the locust management system in Kazakhstan since the formation of the Soviet State and its disintegration after the collapse of the Soviet Union. Similarly, Lockwood et al. [48] analyzed the relative importance of various stakeholders and interests in three case studies (Wyoming in the United States, Eritrea, and Irkutsk in Russia). They observed the changing role of central governments with the deployment of bottom-up approaches and decentralization, and the consequences of locust plagues for farmers in different contexts. From these observations, the authors questioned the historical dependence on distant governments. In the same vein, in the upper right corner of Figure 1, Lecoq [19] proposed what we identify as an opinion paper, which suggested that "*a new approach to locust issues (...) using techniques derived from sociological and anthropological sciences*" is needed. After retracing the history of recent desert locust plagues, Lecoq acknowledged the role played by organizational problems and by the lack of involvement in prevention systems of various stakeholders such as farmers’ organizations: “*the locust is no longer the real problem, humans are the real problem. Every time there has been an outbreak over the last 50 years, the main problem has been human organization...*”. He thus called towards the development of a risk management system, a new governance strategy involving a larger panel of stakeholders, and a better understanding of the role of each of them.
Studies in the lower right corner of Figure 1 used a disciplinary approach, mostly rooted in economic or in socio-economic and development studies with the practical objective of evaluating current management practices and proposing credible alternatives where appropriate. In particular, desert locust campaigns have been submitted to socio-economic evaluations under the impetus of the FAO in the 1990s [63]. These studies aimed to identify who is affected by the desert locust and to what extent, if the current management strategy and control campaigns are appropriate, and what are the costs and the other possible policy responses. Such studies are recognized to be difficult to carry out because of the enormous area that must be studied, the heterogeneity of the potential damages of the pest, the multiple variables that can impact crop production, and the irregular occurrence of outbreaks [64]. Some initial studies criticized the effectiveness of control strategies which are presented as not very cost effective economically, socially, or environmentally [64,65]. Complementary studies were developed later to better integrate the stakes and perceptions of diverse groups at the farm and households levels, and proposed alternatives such as compensation, insurance policies, farmers’ adaptation strategies or biological control [47,66–68]. Lastly, some recent studies demonstrated the long term impact of locust plagues, in particular on health and education, and the lasting damages the plagues caused during early childhood into adulthood [4,69].

To conclude, social science studies interested in locusts are as diverse as natural science studies [24]. As illustrated in Figure 2, they are included in a diversity of approaches (e.g., environmental history, systems approach, sociology, economics, and development studies). They mobilize a diversity of methodologies (e.g., document analysis, quantitative data analysis, economic evaluation, ethnographic approach, reliance on expertise knowledge). They can pursue different objectives, from policy function and structure or efficiency analysis to the inclusion of people's perceptions and social-ecological analysis. They can focus on different scales, from individuals to nations and beyond, they can support existing management practices or adopt a critical approach and try to push towards alternative solutions. While some disciplines are particularly well represented, such as environmental history or economics, others are less so, such as communication, philosophy, sociology, anthropology, and psychology. Their inputs could be valuable to locust science in questioning ethics and epistemologies (see, e.g., the recent work of Lockwood and Sardo [70]), or in observing the issues in the day-to-day management of locusts, during crisis and recession times. For example, communication science could contribute to the development of communication plans to ensure trust over the long run and support coordination during outbreaks.

<figure><img src="image_134.png" /><figcaption>**Figure 2.** Main approaches, methodologies and objectives represented in the studies included in Figure 1 and specifically focusing on locusts (n = 25). Only the boxes and flows represented in two or more papers are represented on this figure. The flows on the left represent which methods are used</figcaption></figure>
by each approach. The flows on the right represent which methods are used to pursue the different objectives. The size of the flows is proportional to the number of papers using this represented flow. For more detail, see Table S1.

# 4. Social Sciences and Tackling Locust Management Challenges

In this section, we highlight how social sciences can help to tackle two of the main challenges of locust management: (1) ensuring coordination and a multi-level governance structure from a local to a very large scale, and (2) maintaining the management system during recession times.

## 4.1. *Ensuring Multi-Level and Large-Scale Coordination*

Most countries recognize that effective locust management requires some form of large scale coordination because control programs are beyond the capabilities of individual landholders alone [14]. At a landscape scale, locusts readily move from one farm to another, so their treatment is often considered a community responsibility. Cooperation at a local scale can be implemented more or less informally or formally, for example informally at a village/town scale or formally through cooperative programs at the county or state level, as in Wyoming, USA [37]. Combating locust outbreaks has also led governments to take responsibility since the latter part of the 1800s, as is the case in Australia or in Argentina [10], or the US in response to the Rocky Mountain locust outbreaks [71] that led to the emergence of some of the first national plant health policies [72].

For species such as the desert locust, which is associated with one of the most ancient organized preventive systems, the great mobility of the swarms imposes the necessity of bilateral, regional and international cooperation [73]. As illustrated by historical studies, some evidence from large-scale collective mobilization against locusts can already be found in Antiquity, with the existence of local locust control specialists and the use of armies to destroy the insects or help with the harvest [74]. The internationalization of the locust problem started as early as the beginning of the 20th century when a large plague in Algeria contributed to the awareness of the international community of the fight against the locust plague [50]. However, the first attempt to find a transboundary solution at a truly international scale only emerged in the 1920s with the first international conference on locust control held in Rome under the auspices of the International Institute for Agriculture and which resulted in an "International Convention for the control of locusts and grasshoppers" [75]. Since that time, it was considered as hopeless to study the locust problem on a narrow territorial basis and cooperation has not ceased to develop to the present day. Many efforts have been pursued to ensure better transboundary coordination. In the 1930s the process of formation of a locust scientific community and the institutionalization of the international scientific fight against the locust took place by means of five international locust conferences, held in Rome (1931), Paris (1932), London (1934), Cairo (1936) and Brussels (1938), resulting in a first conception of a preventive control program for a few locust species by regular monitoring of the outbreak areas [76]. Cooperation became a true reality in the 1950s, with the creation of the desert locust control committee (DLCC) under the aegis of the FAO in 1954, mandated by its Member States to ensure the coordination of monitoring and control activities of the desert locust [73]. Since the creation of the DLCC, FAO has continued to play an active role to promote international locust control cooperation, on the desert locust as well as for many other locust species (i.e., migratory, Moroccan, South American, and red locusts). In present days, the DLCC includes representatives from all the countries affected by the desert locust as well as those which take part in the locust control campaigns, such as various donor countries helping to finance control campaigns. The DLCC is linked in the field by three regional Commissions (created under the auspices of the FAO and at the request of the affected countries): the commission for the Western Area, CLCPRO (the "Commission de lutte contre le Criquet Pèlerin dans la Région Occidentale" created in 2002 to coordinate and finance a regional solidarity on both sides of the Sahel [51,77,78]), the Central Region (CRC), and the eastern region
in Southwest Asia (SWAC), as well as by an inter-state organization: the Desert Locust Control Organization for Eastern Africa (DLCO-EA). These Commissions are mandated to promote all activities, research and training necessary to ensure effective preventive control and capacity to deal with any invasion of the desert locust [73]. However, coordination still presents some weaknesses, even if solidarity and mutual support are well established. In their evaluation of the 2003–2005 desert locust campaign for instance, Brader et al. note that “*A weakness is the lack of clarity concerning the different roles of different actors, and how these relate to each other*” [3].

Given this context, a challenge that the social sciences can help to address is to understand if, when, and how collaboration is effective [79] from local to the international levels. Because of their mobility, locusts represent a collective action problem: they reveal a situation of mutual interdependence between the actors where outcomes depend on the actions of all of these actors. Invasive species, crop diseases, locusts, and other migratory pests have been considered by some authors as a “public bad” [62], a “collective bad” [80], or as a “public good” for their controlling system [81]. These terms all refer to collective action theory [82]. Many authors have noted that desert locust control should be considered as a regional or even international “public good” [83,84], meaning that it is provided as a service accessible to all, including vulnerable people, and supported by those who can afford it and are willing to pay for it, e.g., the general public through governments, donor countries or otherwise. As acknowledged by Toleubayev regarding this “common enemy” [62]: “*agricultural producers are not able to control locusts outside their private plots. This is why many countries treat the control of migratory and highly destructive pests as a public service, comparable with emergency services such as the fire brigade and the police*”. Compared to other archetypal examples of commons such as small-scale forests or irrigation systems, locusts are special since they pose a problem that evades and exceeds the spatial reach and extent of control of the nation state. They thus raise transboundary governance issues as do bluefin tuna fisheries, another archetypal example used to study collective action in large-scale social-ecological systems [85,86]. These transboundary cases have a high number of stakeholders, the temporal and spatial extent of biophysical processes go beyond and are permeable to geopolitical boundaries, and there is often a limited understanding of the complexities of ecological and societal dynamics. Therefore, collective action and collaborative environmental governance are essential [79], which underscores the importance of stronger inclusion of collective action theories [79,82] in the design of governance regimes. In particular, the notion of mismatch can be useful regarding locust governance. According to several authors, many of the problems encountered by societies in managing natural resources arise because of a mismatch between the scale of management and the scale of the ecological processes being managed [30,55,87]. This has been referred to as “scale mismatches”, the “scale challenge”, institutional “fit” or “interplay”, a challenge which is particularly relevant for transboundary issues such as locusts.

Raising coordination issues and the scale challenge, including at a transnational level, is not new in studying locusts. For example, through an historical approach [20], Gomes et al. demonstrated that transnational collaboration was considered fundamental to fight against locusts since the beginning of the 20th century. Through the example of the Iberic peninsula, the authors highlighted the attempts and difficulties in implementing such a coordination effort. Conflicting interests and lack of means led the Spanish actors to blame each other for losses, and the Portuguese actors to blame the inaction of their Spanish neighbors as they observed locust swarms frequently travelling across the border. While a widespread opinion throughout the twentieth century was that Iberians should fight the locusts together, and some evidence support this idea of cooperation, Gomes et al. concluded that “*cooperation and coordination were rare or non-existent*”. In a second example, Lockwood et al. [48], recognized that scale and scale mismatch are fundamental problems in assessing the sustainability of controlling locusts. By focusing on what they called the “geopolitical scale”, the authors insisted on the problem of the historical dependence
of local agents on distant governments that often have the resources, knowledge, and expertise. In parallel, the authors observed a paradoxical trend towards decentralization in locust control characterized by a decline in external support with the aim of increasing responsibilities at the local level. With the notions of "social scale" and "interest scale", they highlighted the diversity of motivations, gains, and losses in different contexts and at several governance levels, for example between farmers, the general public, agrochemical industries, and governments. In a final example, Peloquin [8,51] provided an example of a critical study regarding the concept of scale mismatch. Similar to other political ecologists, rather than taking the mismatch between institutions and ecosystems as given, he critically investigated why and how given socio-ecological dynamics become adopted as management mandates by agencies, and what particular technological or institutional arrangement is favored by these configurations. Taking the example of locusts, he illustrated how the French colonial Empire prioritized organizing against the desert locust during the Second World War because the spatial extent of the insect provided an ideal context in which to reinvent the spatiality and legitimacy of the French Empire as a transnational and constructive federation during a geopolitical crisis [8]. Similarly, Roy describes how the existence of two colonial empires on the African continent—French in the West, English in the East—explained for decades the lack of cooperation at the scale of the continent regarding the management of the desert locust [21].

## 4.2. *Maintaining Vigilance during Recession Times*

The second main challenge is to maintain the infrastructures needed for sustainable locust management during recession times. Locusts are temporal, alternating absence with peaks of high activity that must be rapidly managed. Major outbreaks can be separated by several decades, depending on the species and on the maintenance and efficiency through time of the management system. Such long-term environmental problems raise the issue of funding, support provision, and knowledge maintenance over substantial time frames [79]. For locust managers, an acknowledged challenge is the maintenance of an operational control system and a set of elements: (i) available and functional material for survey and control (e.g., vehicles, planes, insecticides) and (ii) available and trained staff during recession times. Funding is of course essential to ensure the maintenance of these two crucial elements.

Some studies on locusts have tackled this issue. As illustrated in Figure 3, Lecoq was one of the first to explicitly refer to an institutional cyclicity in the case of locusts [88]. Making an analogy with locust phase polyphenism, he characterized an alternation between two institutional phases: a motivation phase associated with important funding in the face of an emergency situation, and an oblivion phase during recession times when "*the memory of the invasion fades, funding is reduced below an operational level, specialists are dispersed, and motivation wanes*". This "vicious" cycle [60] thus refer to a situation in which one is locked in a complex chains of events that reinforce themselves through a feedback loop and that has detrimental results. It is typified by the desert locust but can also be observed in Madagascar for the migratory locust [14] and in the South American locust [89]. When looking back at the desert locust invasion of 1987–1989 [21], Roy notes that when the severity of the threat diminished, vigilance is decreased. Under other constraints and faced with other emergencies, government authorities gradually considered locust control action a secondary interest. Funding from government partners was deferred, then reduced or even suspended, leading to a decrease in operational potential, staff and non-renewed equipment that degrades. Through an insidious process, managers worried about the possible loss of their positions and tended to hide the seriousness of the decline in field staff and resources from the government on which they depended. Roy described the loss of knowledge induced by the dismissal or retirement of field staff and researchers as "*one of the most devastating effects (...) as equipment can be renewed and insecticide stocks replenished in a matter of months, but the loss of these experienced and dedicated field staff is an irretrievable loss*—it will take many years to train their successors, but the trainers themselves have become
scarce". Roy and Lecoq thus asked this question which remains topical [21,88]: how to get out of this vicious cycle? How can an operational structure be maintained against an intermittent scourge? We add this complementary question: how to identify emerging institutional weaknesses before they reveal themselves mostly during a time of crisis?

<figure><img src="image_135.png" /><figcaption>**Figure 3.** The phase theory applied to institutions: a representation of the vicious cycle alternating a motivation phase and an oblivion phase in locust management. Adapted from Lecoq, 1991 [88].</figcaption></figure>

The French sociologist Doré and colleagues studied the maintenance of vigilance during recession times [9,90]. In a time when the efficiency of the preventive control system was questioned, their work was an attempt to understand the failures of the preventive system that led to the 2003–2005 desert locust invasion. More than a lack of trained human resources, Doré et al. highlighted the shortcomings of international involvement which, by seeking to rationalize expenditures, created a slow and under-mobilization of logistical and human resources. Bilateral and regional assistance mechanisms can mitigate these shortcomings to some extent. For example, the authors discussed the necessity to integrate the complexity of organizational and governance issues in a multi-level actor system, and to no longer think of international action only as the game of war against locusts, but also as a permanent biovigilance, which equitably distributes risks among the players [90]. Stopping the erosion of vigilance thus relies on the perpetuation of a difficult coordination among heterogeneous actors: solitarious desert locusts, the information network that connects the managers, and research projects play a central role in this maintenance over time. These multiple components allow the managers to have more continuity and free themselves from having to act in a crisis mode [9]. While Gay et al. also illustrated the role of funding institutions’ awareness as a facilitating factor for cyclic locust plagues, they argued that loss of skilled field agents was of primary concern and their recommendations thus included plague simulation exercises [61]. Most locust response systems are subject to this cyclic loss, but awareness has been building for several years and locust managers are now trying to take better account of these issues. For instance, in the case of the desert locust, CLCPRO has implemented risk management plans including simulation exercises between outbreaks, a monitoring and evaluation plan to enable actors in the system to know in real time and at the country level, the state of equipment, staff or pesticides, and a communication plan (http://www.fao.org/clcpro/fr/, accessed on 10 May 2021). More recently, a financing system designed to address the various levels of desert locust infestations began to be developed [91]. There are also successful examples such as the Australian Plague Locust Commission (APLC) in Australia. The APLC has been funded continuously by four Australian member states from 1974. This funding supports the maintenance of their structures and keeps them prepared to immediately react in the event
of an alert [92]. We can speculate that this stability is explained both by the fact that the relatively high frequency of Australian plague locust outbreaks helps to maintain the motivation of the actors, and that it concerns a single country that is politically stable and has a high GDP.

These spatio-temporal challenges of governing transient socio-environmental problems are not specific to locusts and can be analyzed using the concept of “temporal misfit” or “temporal-scale mismatch” between biophysical systems and institutions [30,93]. A temporal misfit can be defined as a case in which an institution is formed too early or too late to cause desired ecosystem effects, or if conflicting time frames exist between policy-makers and those of the environment. In the literature, such temporal governance challenges can be found for a diversity of risks and disasters, ranging from epidemics [94] and wildfires [95] to nuclear risk [96]. As illustrated for governing epidemics [94], the dominance of an outbreak narrative can have drawbacks such as marginalizing narratives that emphasize long-term structural, land use, and environmental changes, and local knowledge. The risk of loss of knowledge and expertise has also been observed in the case of nuclear risk [96]. Many nuclear employees and experts who designed, constructed, and currently operate existing nuclear power plants are now approaching retirement. A consequence is the potential loss of a substantial amount of critical nuclear energy knowledge. In response, nuclear organizations conduct knowledge loss risk assessments, evaluate the consequences of the loss of critical knowledge and skills, develop action plans to retain this knowledge, and use this knowledge to improve the skills and competencies of new and existing workers. Knowledge loss may be related to cyclicity, as described for example in bank lending behavior [97]. In this case, the institutional memory hypothesis speculates that cyclicity may be driven by a deterioration in the ability to recognize problems: institutions may tend to forget the lessons they learned as time passes since their last learning experience with the problem. Studies on risk perceptions have shown that personal experience of a natural hazard and trust in authorities has a substantial impact on risk perception. However, perceiving a risk is not sufficient to guarantee that an actor will take action; action depends on motivation, responsibility, and ability to respond [98].

In the case of locusts, these elements question the dominance of an outbreak narrative, the frequency of learning experiences, and the fact that they may be growing increasingly apart in time due to the implementation of effective preventive strategies. A common trap with preventive strategies is that when you are successful in prevention, there seems to be no need for prevention: the perception of the risk disappears, and with it the feeling that investment in prevention systems must be maintained. Bödin argues that the management of such transient environmental problems requires rapid responses, and thus the mobilization of relevant actors organized in ad hoc collaborative networks [79]. In such conditions, studies on collaborative governance have demonstrated that more-centralized networks with specific actors acting as leaders by distributing and coordinating tasks were more favorable [99], if actors already agree on what needs to be done, share inter-personal and inter-organizational trust, and are willing to comply with the identified responses. This of course requires underlying, dense and longer lasting collaborations, even during the absence of locust plagues.

**5. Conclusions: Engaging Social Sciences to Improve Sustainable Locust Management**

Social sciences are a vital component, along with the natural sciences, for effective and sustainable locust management, including decision-making, planning, implementation, and management both during crisis and recession times. In this paper, our objective has been to clarify the role played by social sciences and inspire uptake of the social sciences in locust research and management. We have highlighted the diversity of possible applications and contributions, as well as some of the existing contributions to respond to the main challenges faced by locust managers around the world. We have also pointed out some shortcomings, such as the limited questioning of locust management narratives and underlying epistemologies. Examples of studies on other large-scale and erratic socio-
environmental problems such as epidemics, hurricanes, and wildfires could shed new light and perspectives on the present and future challenges faced by locust managers. In particular, some long-term environmental and social changes may challenge the way locusts were previously managed. These changes include not only land-use and climate change and rising environmental concerns, but also renewed environmental governance models that include more bottom-up and participative approaches, and increasing calls for social justice [70]. Such changes call for new ways of interacting and living with nature and with locusts. They question the dominant narratives focusing predominantly on techno-scientific control, mobilizing war rhetoric or continuing to present locusts as a biblical plague. The social sciences can help take a step towards making salient what we often take for granted such as taking into account only techno-scientific parameters, highlight the impact of variable social aspirations and political divisiveness, and invent the future of sustainable locust management.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/article/10.3390/agronomy11050951/s1, Table S1: Detailed categorization of the papers referenced in Figure 1 and graphically illustrated in Figure 2 (n = 25).

**Author Contributions:** Conceptualization, C.T., J.M.A. and A.C.; validation, J.M.A. and A.C.; writing—original draft preparation, C.T.; writing—review and editing, C.T., J.M.A., M.L. and A.C.; visualization, C.T.; supervision, J.M.A. and A.C.; project administration, A.C.; funding acquisition, A.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Foundation for Food and Agricultural Research, grants no. 593561, by the Global Locust Initiative and by the Swette Center for Sustainable Food Systems.

**Acknowledgments:** Research reported in this publication is supported by the Foundation for Food &Agriculture Research, Grant ID: 593561, the Global Locust Initiative and the Swette Center for Sustainable Food Systems at Arizona State University. The content of this publication is solely the responsibility of the authors and does not necessarily represent the official views of the Foundation for Food &Agriculture Research.

**Conflicts of Interest:** The authors declare no conflict of interest. Given their role as Guest Editor, Michel Lecoq & Arianne Cease had no involvement in the peer-review of this article and had no access to information regarding its peer-review.

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Article

# A Swarm of Injustice: A Sociopolitical Framework for Global Justice in the Management of the Desert Locust

Jeffrey A. Lockwood <fnref n="1" />,* and Michael Christopher Sardo <fnref n="2" /> ID

**Citation:** Lockwood, J.A.; Sardo, M.C. A Swarm of Injustice: A Sociopolitical Framework for Global Justice in the Management of the Desert Locust. *Agronomy* 2021, *11*, 386. https://doi.org/10.3390/agronomy11020386

Academic Editors: Michel Lecoq and Arianne Cease

Received: 22 January 2021
Accepted: 19 February 2021
Published: 21 February 2021

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<figure><img src="image_136.png" /></figure>

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

**Abstract:** In recent years, scientists and managers have advocated for the integration of the social sciences (particularly political science and economics) and the humanities (particularly moral philosophy) with the natural sciences (particularly entomology and ecology) in developing a full understanding of locust-management programs. In this paper, we pursue such a synthesis by using the desert locust (*Schistocerca gregaria*) as an exemplar case. After an overview of this insect's biology, ecology, and management, we provide a brief summary of the standard, moral theories (utilitarianism, deontology, and virtue ethics) and consider their shortcomings with regard to developing a framework for understanding the socioeconomic complexity of locust management. Next, we address some of the models of global justice and focus on two fundamental questions: Who is a moral agent with regard to desert locust management, and how should we justly distribute the responsibilities among agents during preventive and reactive modes? After identifying the agents, we use a fourfold set of principles to construct a framework for locust management consistent with global justice and apply this conceptual system to two hypothetical scenarios. We conclude with some observations from political philosophy that offer progress toward a comprehensive and applicable theory for locust management in the context of global justice.

**Keywords:** locust plagues; preventative and reactive programs; moral agents; capacity-and-capability model; social connections model; responsibility; global justice

## 1. Introduction

Locusts (Orthoptera: Acrididae) are among the most devastating pests in human agriculture. This common name for these insects is derived from the Latin *locus ustus*, meaning “burnt place,” to describe the condition of the land after a swarm has passed. These insects have caused serious damage to crops and forage across the globe, and their depredations have become the basis for legends, myths, and—in recent times—staggeringly complex, multinational control programs. Aside from pandemics, no biological phenomenon afflicts a larger expanse of the Earth than locust plagues. For example, the desert locust, *Schistocerca gregaria*, spans 60 countries, generating cooperation (and conflict) across three continents— and arguably on all six inhabited continents if we include the role of international donors during insect-driven, humanitarian crises.

Human efforts to manage locust outbreaks entail the integration of virtually all fields of academic inquiry. Understanding the insects themselves requires the study of biology (evolution, genetics, biochemistry, physiology, and anatomy), while their ecology demands an understanding of atmospheric science, chemistry, soil science, hydrology, and botany, among other fields. The movement of locusts across borders necessitates the inclusion of political science and economics, along with cultural and anthropological research. Grasping the complex international aspects of locust management also requires the study of history, including the legacy of colonialism. And the conflicts and harms arising from

<footnote n="1">¹ Department of Philosophy and Religious Studies, University of Wyoming, 1000 E. University, Laramie, WY 82071, USA</footnote>

<footnote n="2">² Department of Politics, Occidental College, 1600 Campus Road, Los Angeles, CA 90041, USA; msardo@oxy.edu</footnote>

<footnote>* Correspondence: lockwood@uwyo.edu</footnote>
locust infestations raise important questions with regard to environmental ethics and global justice.

Such complexity calls for an overarching framework for understanding the locust-human nexus, which integrates interdisciplinary scholarly research and real-world practices. While universities, government agencies, and international organizations "talk the talk" of interdisciplinary collaboration, locusts provide an urgent test of our willingness and ability to "walk the walk". In particular, we argue that the scale and magnitude of locust swarms raise crucial normative questions of global justice that cannot be answered by natural scientific inquiry alone. Such questions include the scope of moral and political obligations, whether transnational inequalities constitute a question of justice, and the proper agents responsible for implementing the standards of global justice. However, while the global justice literature often engages environmental questions, such as natural resource inequalities and climate change, locust plagues have garnered little attention in that field. In this paper, we hope to make a modest contribution—along with those who have already taken the first, small steps—toward a desperately needed collaboration of the natural sciences, social sciences, and humanities to address an ongoing and worsening cause of human suffering.

In this paper, we review the ecological and economic relationships between humans and locusts, with particular attention to why the challenges with respect to pest management cannot be mitigated solely in terms of the natural sciences, and how these shortcomings are a matter of justice. We briefly review the triad of standard ethical theories (utilitarianism, deontology, and virtues) and make the case that features of locust population dynamics require us to apply theories of global justice. From this argument, we then address the two fundamental questions of who an agent of justice is and how responsibility should be fairly distributed among these agents. We conclude with the application of the most compelling theoretical frameworks to simplified but realistic case studies to illustrate how the principles of global justice could inform our policies and actions.

## 2. Background: Entomology, Society, and Politics

### 2.1. *Locusts and Humans*

#### 2.1.1. Locust Biology

Locusts are those species of grasshoppers that exhibit behavioral, anatomical, and physiological "phase changes" associated with aggregation and migration under crowded conditions. At high population densities, these insects undergo a transformation from the solitarious to the gregarious phase, during which they shift from avoiding one another to seeking close proximity with conspecifics. In the gregarious condition, the immature hoppers (nymphs) aggregate in dense bands that march across the habitat, and the adults form swarms that fly long distances [1-3]. Tactile and olfactory cues are used by the insects to assess population densities and thereby initiate the reversible phase transformations [4].

While some locust species are chronic hazards to agriculture and require treatment in most years, many of the most serious pests exhibit erratic population dynamics with periods of low densities punctuated by irruptive population growth requiring emergency interventions to avoid disastrous crop losses [5-7]. In this paper, we will focus attention on the prototypical, widespread, and damaging species, the desert locust, which extends across 29 million km² from India to Mauritania [7].

Like many other locust species, *S. gregaria*'s population dynamics are driven by weather. In particular, precipitation is primarily responsible for indirectly triggering the gregarious phase by generating abundant vegetation in the desert habitats where the solitarious locusts chronically persist. In conventional terminology, a period of low population density in nonagricultural habitats is called a recession. An outbreak is characterized by localized, small swarms with most populations remaining solitarious. During an upsurge, continuing regional rains allow locusts to increase in density across multiple generations with more frequent swarming. Perhaps 20% of upsurges develop into plagues with swarms infesting an entire region causing extreme damage to crops and pastures [8].
2.1.2. Locust Management

The management of the desert locust involves two, distinct strategies: the chronic,
localized management of incipient outbreaks to prevent large-scale population increases;
and the acute, reactive, large-scale treatment of hopper bands and adult swarms when
prevention fails. The challenge in shifting from reactive to preventive modes strategy is
the so-called “vicious cycle” [9–11] in which funding is abundant during plagues due to
an urgent need to mitigate suffering, while between these humanitarian crises, there is
diminished support for surveillance and tactical treatments.

During plagues of the desert locust, millions of people relying on subsistence farming
may require food aid [7]. The socioeconomic damage is further manifest as pastoralists
sell their livestock at deflated prices to meet acute needs. As such, the harm to agricul-
turalists can extend for years as they incur debt or lose their land entirely. In addition,
there is a negative impact to child education and health that persists well beyond the
locust plague [12,13]. Reactive-control programs rely heavily on broad-spectrum chemical
insecticides applied by aircraft and ground sprayers. Positioning equipment and supplies
in pursuit of fast-moving swarms is a significant logistical challenge. Biological insecticides
have made some inroads, but because these pathogenic products are largely restricted to
locusts, the market is erratic and requires dramatic, rapid increases in production during
an upsurge or plague. Moreover, once a plague has subsided, these materials cannot be
used for other pests, and storage stability is limited. While some broad-spectrum chemical
insecticides can find agricultural uses after a reactive program, large stocks of obsolete,
environmentally undesirable or banned insecticides have accumulated in locust-afflicted
countries [14].

A strategy of preventing locust plagues through locating and treating hopper bands and adult swarms during the outbreak phase [15,16] is considered to be the most economically efficient use of resources [17–19] (for a dissenting view, see [5]). Satellite imagery combined with geographic information systems is used to find green vegetation that signals the possibility of breeding conditions in desert areas, as locusts encounter abundant food and moist soil for their eggs [20]. But ultimately, scouts must go into the field to assess infestations and apply localized treatments—this a weak link in that the locusts often arise in places that are extremely remote and locations with military hostilities or minefields from previous conflicts [14]. The actual efficacy of preventive programs in most countries within outbreak areas can be called into question by consideration of the frequent upsurges and plagues that have developed in the last 35 years.

2.2. *The Desert Locust in a Sociopolitical Context*

2.2.1. Need for New Approaches

The ecological and social challenges arising from preventive and reactive locust-management programs are too interdependent to be addressed through the natural sciences alone [21]. Although biologists have pursued studies of transboundary coordination, risk management, stakeholder strategies, and economic cost-benefit analyses, social scientists have rarely been involved, with a few laudable exceptions (e.g., [10,22–25]). As argued by Zhang et al., “The sustainability of locust and grasshopper control must be better assured by considering not only scientific and technical aspects, but also socioeconomic mechanisms involved in the management of these pests” [7] p. 27. However, there is a further consideration. A sound system of locust management must be not only efficacious but moral, as unjust demands on countries and regions are sociopolitically unsustainable.

The Food and Agriculture Organization (FAO)'s proposal for an improved financing system illustrates the problem of analyzing desert locust management without regard to ethical considerations [26]. The prospectus includes a plan for funding during various periods of locust population dynamics, but there is no consideration of who ought to be responsible for providing support or how this responsibility should be fairly allocated. In this example, as in many others, there is a valuable, descriptive critique (i.e., what is being done) but little or no normative analysis (i.e., what should be done).
In a similar sense, intense conflicts over the goals of desert locust management are exemplified by the 2020 exchange between Tom, US Ambassador and Permanent Representative, United Nations Rome Based Agencies, and Metlerkamp, research fellow at the Environmental Learning and Research Center Rhodes University. Although competing socioeconomic ideologies were presented, neither side in this debate went beyond simple, normative assertions (i.e., that industrial or agroecological values were to be preferred) [27,28]. As such, the competing and compelling ethical foundations were largely obscured by political rhetoric.

The current locust plague reflects ecological and political conditions [29], including armed conflicts among weak states in the Middle East and eastern Africa, which precluded effective preventive programs following heavy rains [30]. The early outbreaks went undetected, allowing swarms to develop [31]. Using a spatially explicit multiagent model, Gay et al. [11] found that a preventive program can be nullified with just 5% of the territory having limited access. The study concluded that plagues are most likely to originate in weak states with larger areas inaccessible to pest managers. Add to this the reluctance of donor nations to provide funds to countries that engaged in terrorism and human-rights abuses (e.g., Sudan), and the potential for locust outbreaks to emerge undetected and unimpeded is significant [14]. And this is not a new problem, as the 1986–1989 plague was substantially attributable to a lack of early intervention due to armed conflict in the primary locust breeding areas of Eritrea and Sudan [14].

Natural disasters have been analyzed using various risk governance, operational, and funding models (e.g., [32–34]), but such theories rarely consider locust plagues. Although locust control is increasingly viewed as being the management of a natural hazard [7], the desert locust presents several unique features that must be considered in developing any viable, socioecological analysis. These qualities include ecological dynamics, geographic scale, geopolitical complexity, and socioeconomic factors.

### 2.2.2. Distinctive Features of Locust Plagues

With respect to ecological dynamics, since 1860 there have been 10 upsurges lasting 1–4 years (mean = 2 years) and nine plagues lasting for 1–22 years (mean = 10 years) [8]. This means that recession periods are the norm and can last more than a decade. During recessions, international funds, along with regional, national, and local resources are shifted to urgent problems rather than outbreak-prevention programs for locusts. However, it is important to recognize that past ecological patterns may not be reliable indicators of future dynamics, as climate change is likely to exacerbate the unpredictability and intensity of plagues [35,36]. With rising temperatures, insect development is accelerated (locusts typically take about a month from hatching to fledging) [4] and flight performance (speed and distance) may be enhanced [8]. Extreme weather events make forecasting locust dynamics increasingly difficult. For example, despite a general trend of increased droughts in Africa [37], the current plague developed during unusually heavy rains from two tropical cyclones in the Arabian Peninsula in just 5 months [29,38]—phenomena linked to the rapid warming of the Indian Ocean [36].

In terms of geographic scale, the desert locust afflicts 10% of the human population [39]; only pandemics have a wider scope. The current plague involves nine countries (Ethiopia, India, Iran, Kenya, Pakistan, Somalia, South Sudan, Uganda, and Yemen) with swarms moving into parts of six other nations [40]. Food shortages may soon resemble those in 2003–2005, when crop loss exceeded 80% in Burkina Faso, Mali, and Mauritania despite the treatment of 13 million ha at a cost of USD 500 million [41,42]. Upsurges and plagues produce mismatched scales in which the potential for harm is widespread and control operations must be dispersed across enormous areas to track swarms moving up to 150 km/day, but damage is highly concentrated wherever locusts descend to feed. With both reactive and preventive management, the costs accrued in one place yield benefits elsewhere. Individualizing costs and collectivizing benefits becomes a serious challenge in terms of funding and cooperation.
The spatial scope of the desert locust leads to geopolitical complexity. A brief overview provides a sense of the international efforts [26]. The Food and Agriculture Organization (FAO) of the United Nations has established three Regional Commissions for Locust Control (western, central, and eastern, totaling 56 countries) that obligate member states to develop monitoring and control programs through national centers or ministries of agriculture. The FAO also hosts: (1) the Desert Locust Control Committee, which is composed of national representatives and coordinates monitoring and control plans; (2) the Desert Locust Information Service, which provides data, analyses, and forecasts; and (3) the Emergency Centre for Transboundary Plant Pests, which mobilizes emergency aid provided by donors such as USAID (USA), DGIS (the Netherlands), CIRAD (France), CIDA (Canada), SIDA (Sweden), ODA (UK), and GTZ (Germany) [14]. Different countries and cultures give rise to various challenges, such as the implementation of control programs during Ramadan, the acceptability of locusts as human food, the reluctance to accept foreign aid, and the movement of swarms across borders, which erodes fragile relations between hostile countries [43].

Socioeconomic factors exacerbate the spatiotemporal challenges. Standard economic analyses of desert locust-management programs have been criticized for omitting the perspectives of nomads, the value of food security, the costs of environmental damage, the sociological constraints in different countries, and the humanitarian benefits of pest management [14]. In large part, these insects are found in impoverished nations where colonial legacies have created weak national governments with continuing dependence on donors for the costs of preventing or controlling locust plagues [43]. In turn, perverse economic incentives may delay a poor nation's response to outbreaks in order to generate more foreign aid, given the opportunities for lucrative contract services during a plague. If the afflicted people are subsistence agriculturalists, then other nations, and even the urban centers within an infested country, are not directly harmed and assistance becomes less urgent, particularly if locust control competes with more dire threats (e.g., the current plague is unfolding at the same time as the COVID-19 pandemic).

In sum, it is evident that the ecological, geographical, geopolitical, and socioeco-
nomic factors that shape the course of desert locust population dynamics and human
responses, contribute in clear but complex ways to the unjust distribution of both the costs
of preventive and reactive programs and the harms resulting from the failure of these
interventions.

3. Locust Swarms as a Question of Global Justice

3.1. *Locusts and Justice*

3.1.1. The Limits of Individualistic Ethical Theories

Traditional theories of ethical and moral obligation identify principles that determine the proper moral action for individuals to take. Utilitarian principles emphasize the consequences of action, arguing that the moral action is that which produces the greatest good for the greatest number [44], while deontological principles defend absolute duties that must be followed regardless of their consequences [45]. The third traditional school of thought, virtue ethics, takes the position that we should cultivate character traits through practice so that individuals will develop their fullest, human potential [46].

These ethical positions can fruitfully expand the scope of one's moral obligations. For example, Singer has argued, because pleasure and pain are universal, the obligation to reduce suffering transcends national boundaries [47]. There is no difference, in his framework, between letting a child drown in front of you for fear of damaging your expensive clothing and purchasing expensive clothing in the first place, when that money could be used to alleviate starvation and disease in other countries. Therefore, he concludes, "If it is in our power to prevent something bad from happening, without thereby sacrificing anything of comparable moral importance, we ought, morally, to do it" [47] p. 231. A similar argument could be reached through deontological reasoning, contending that we have an absolute duty to preserve human dignity regardless of consequences. However, as
O'Neill (1993) [48] contends, such duties are “imperfect,” meaning that while we have an absolute duty not to directly impair the dignity of another person ourselves, promoting the dignity of distant others would be beneficent, but not morally obligatory. While virtue ethics presents a more difficult case, as such theories emphasize the particularity of ethical communities and traditions [49], Van Hooft argues that cosmopolitanism can be considered a virtue in a globalized world, in which individuals view themselves as citizens of the world and see their moral obligations extending globally [50]. Therefore, whether taken as a moral obligation to prevent suffering, an imperfect duty to promote human dignity, or as an fulfilling the virtue of cosmopolitanism, the traditional ethical “triad” can provide good moral reasons why individuals should seek to provide aid—whether preventative or reactive—to those suffering from locust swarms.

While a detailed analysis of ongoing debates between these rival theories is well beyond the scope of this article, we note that there are significant challenges in applying these principles to desert locust management. For example, utilitarian calculations could in fact argue that locust plagues (we will use this term henceforth to include upsurges) are not worthy of moral consideration because resources could be more fruitfully put toward assisting refugees, battling climate change, or providing vaccinations against infectious disease. A similar line of argument was implicit in Tom's impassioned argument for using chemical insecticides to suppress the current desert locust plague, along with shifting global agriculture to an industrial model so as to produce abundant food at a low cost to feed as many people as possible [27]. Similar challenges face deontological approaches, since humanitarian assistance would qualify as an imperfect duty: we ought to practice charity but we do not have a duty to donate to every person or nation requesting our assistance. Thus, for a locust-control program, deontology offers no way of determining how the general duty to assist others in need should be instantiated, nor is it the case that anyone is unethical for not providing aid to locust afflicted people if one discharges one's charitable duty in other ways. The result is an impotent demand that “somebody should do something,” which is a common response during humanitarian crises. Virtue theorists fare little better, given widely divergent conceptions of the meaning of the virtues across different cultures. What constitutes the “good life”—or the full realization of human potential—for one culture or community may not for another, raising concerns of paternalism or cultural imperialism.

Additionally, moving from individual moral obligation to questions of collective action and responsibility creates further challenges. We cannot simply scale up these systems to make sense of the ethical obligations of collectives (groups play a vital role concerning the responsible and effective management of the desert locust) for two important reasons. First, there are collective duties or responsibilities that a society is obligated to meet, but that no individual is blameworthy for failing to fulfill (e.g., a society ought to provide education and healthcare to people, but no particular person is ethically required to become a teacher or doctor). Second, because collectives are internally diverse with respect to power, influence, privilege, and causal relation to any particular harm, the question of allocating responsibility becomes vital. To take Singer's example of a child drowning in a river: If a dozen people see the child struggling, the problem of who should act gives rise to questions such as, "Who is trained in lifesaving?" "Does anyone have a special relationship with the child?" "Did someone cause the dire situation?" and "Can we form a human chain to reach the child and thereby reduce individual risk?" Given the cost of acting (jumping into the river to save a drowning child or donating funds to save hungry farmers), there is an incentive to wait for others who are more willing and able to intervene [47].

As such, cases of shared responsibility require a framework for justice. This is not to say that justice is devoid of utilitarian or deontological elements, but that the standard theories are not the principled foundations for collective, moral, and political action. Our more fundamental concern, however, is that relying upon these moral theories in isolation overlooks the nature of locust plagues as an injustice. Given the complex cultural dynamics within which the prevention, management, and harms of locust plagues are embedded,
individuals trying to fulfill their moral obligations—whether to alleviate suffering, promote human dignity, or practice the virtues—find that their actions are mediated by social, political, and economic forces beyond their control. This can be a disempowering realization, leading otherwise well-intentioned individuals to lament that there is nothing they can do to solve the problem. More fundamentally, these ethical approaches tend to treat human suffering in a vacuum, as an exogenous fact or tragedy that must be morally remedied like a tornado devastating a farm community. Our contention, however, is that locust plagues are better understood as injustice arising through the interaction of natural and human processes.

### 3.1.2. Injustice: Beyond Bad Luck

Not every inequality connotes an injustice. Some people are taller or younger than others and some countries have better soil or more minerals than others, and these unequal qualities are not unfair. Likewise, in the context of natural phenomena, inequalities may arise because someone is struck by lightning or a region is more prone to earthquakes. Given the sentiment expressed by Hayek that justice “ought to be confined to the deliberate treatment of men by other men” [51] p. 163, it is tempting to treat locust plagues, and other natural disasters, as misfortunes, tragedies, or bad luck, rather than injustices. Such thinking misunderstands the nature of justice and the particular injustice of natural disasters in fundamental ways.

Justice is often understood in distributive terms. Such a conception has a long pedigree, dating to Aristotle’s argument that justice entails treating equals equally and unequals unequally, when such inequalities are morally relevant (e.g., sentience or nonsentience rather than male or female). Sandel helpfully summarizes this conception as how a society “distributes the things we prize—income and wealth, duties and rights, powers and opportunities, offices and honors,” or ensuring that society “gives each person his or her due” [52] p. 19. To understand locust plagues as injustices, under this framework, is to highlight the inequitable distribution of harm they generate.

Rawls’ conception of “justice as fairness” is perhaps the most well-known and influential account [53]. This theory begins with a thought experiment: Imagine that you are behind a “veil of ignorance” such that you do not know your particular characteristics (nationality, ethnicity, wealth, gender, etc.) and you must develop the principles that will apply when you reenter the world. Rawls maintained that in this “original position,” rational individuals will select three impartial rules of governance: the Liberty Principle granting all individuals a right to basic freedoms, the Equality Principle granting each person a right to the same opportunity of acquiring resources as others with the same natural abilities, and the Difference Principle allowing inequalities as long as they benefit the worst-off individuals. Rawls’ goal is to nullify “the accidents of natural endowment and the contingencies of social circumstances” that are “arbitrary from a moral point of view” [53] p. 15. Such thinking can be applied to the question of locust plagues, by considering the contingencies of birth (e.g., geography) that make one more susceptible to suffering harm. Resources should be distributed to benefit those worst off in society, to nullify the negative effects of these contingencies.

Justice should not only be understood in terms of material distributions, however. Following Young (1990 [54] p. 37), injustices are more fundamentally understood as social and institutional conditions that create “oppression, the institutional constraint on self-development, and domination, the institutional constraint on self-determination” [54] p. 37. Goodhart similarly describes injustices as “deformit[ies] in social relations [that] create, sustain, or contribute to subordination” [55] p. 143. In this conception, the true injustice of locust plagues lie in the social, political, and economic institutions and structures that create unequal patterns of vulnerability, adaptive capacity, and suffering in the first place. In either Rawls’ or Young’s conception, locust plagues should not be written off as mere tragedies of nature to be remedied, but as injustices generating moral and political responsibilities for two crucial reasons.
First, human influences may make natural events more frequent, severe, or prolonged. Hurricanes, floods, droughts, and wildfires occur without human intervention, but anthropogenic climate change is worsening these disasters. In terms of acridid population dynamics, rangeland grasshopper outbreaks are natural phenomena in the western US, but the use of broad-spectrum insecticides that eliminate parasites and predators increases the duration and intensity of these infestations [56]. With regard to desert locusts, upsurges have been attributed to both the failure of countries to implement preventive management methods [14,29] and the triggering of population increases as a consequence of climate change [35,36].

Second, we must consider the allocation of the economic and social costs of natural disasters, which may be unjustly distributed even with random events. For example, the damage of an earthquake or hurricane may be far greater for people lacking the resources to access healthcare or rebuild houses. However, even if humans are partially or wholly responsible for a natural disaster, there is no injustice if those who allowed the problem to develop (e.g., by neglecting to take steps to prevent harm) or benefited from fostering the adverse environmental conditions (e.g., by accumulating comforts and conveniences that emit greenhouse gases), accrue the costs. However, with phenomena such as climate change and locust plagues, the costs are primarily borne by those lacking wealth and power—impoverished countries, former colonies, unstable governments, and subsistence agriculturalists who did not neglect to act or benefit from inaction [7,14,30,43].

Therefore, locust plagues should be understood as what Shue calls a compound injustice, which occurs “when an initial injustice paves the way for a second, as when colonial exploitation weakens the colonized nation to such an extent that the colonizer can impose unequal treaties upon it even after it gains independence” [57] p. 4. In the case of locust plagues, existing inequalities in the global political-economic order—themselves legacies of colonialism [58]—leave the already-vulnerable both more susceptible and less equipped to effectively respond, manage, and adapt to locust plagues.

To treat locust plagues as mere bad luck, would, following Shklar, impose a “sense of tragic inevitability upon events that are in fact entirely (or at least substantially) amenable to purposive human alteration” [59] p. 70. This fatalism then obscures questions of responsibility and ultimately reifies existing inequalities as natural. Similarly, Erskine contends that retrospective ascriptions of blame after international, natural disasters can distract from addressing how responsibilities should be distributed in the future [60]. Who has a moral duty and what constitutes a just allocation of such responsibilities are as vital as questions about logistics, financing, and politics. Dealing with prospective responsibilities to avert future crises is more important than investing energy into assigning retrospective culpability when nothing (or too little) was done. Vague references to the failure of the “international community” are singularly unhelpful. It is the purpose of this paper to open a conversation as to how we might prospectively identify the moral agents and just distributions of responsibilities in the context of a sound sociopolitical and ecological understanding of desert locust management.

### 3.1.3. The Challenge of Global Justice

The normative concerns with desert locust management become even more challenging when placed in their global context. As Zhang et al. argue, “Robust mechanisms need to be put in place to ensure continuous financial support at national and international levels so that treatment programs can be put in place in a timely manner as part of successful strategies of sustainable preventive management” [7] p. 26. If one’s concern is justice, desert locust management inevitably raises questions of how to give “each person his or her due.” Who should provide this financial support: domestic governments, foreign governments, international organizations, or nongovernmental organizations? To whom should such financial support flow? How should different projects be prioritized? What do citizens of one nation-state owe to citizens of distant ones? If justice concerns not only distributive questions, but also, as Young and Goodhart contend, questions of social
structure, institutional domination, and oppression, these questions are even more vex-
ing [54,55]. We must ask what obligations do nation-states (or their citizens) have to reform
unjust institutions in other nation-states, or would such actions be themselves unjust? If
the institutional structure in question is the global political–economic order, including
the structure of global trade, international patent law, and humanitarian assistance, what
obligations can individuals realistically and meaningfully have with respect to such a
structure? The debate over such questions in the literature on global justice is voluminous,
and our treatment will necessarily be schematic. However, our contention is both that this
body of literature can be fruitfully used to study the ethical challenges of desert locust
management, and that the question of desert locust management can add further richness
to the relatively abstract discussion of global justice.

Much of the debate concerns whether justice is even a meaningful concept at the
global level, or if the scope and boundaries of justice should be restricted to more formal
political communities. We begin with a consideration of cosmopolitan views and then
address statist views.

Cosmopolitans, as we have earlier noted, argue that both membership in a political
community and physical proximity are both morally arbitrary when evaluating one's
moral obligations. Emblematic of this line of argument is Singer's insistence that there is
no morally relevant difference between letting a child drown within eyesight and letting
a child starve to death on the other side of the world [47]. One has a moral obligation to
alleviate suffering, wherever it occurs.

In an increasingly globalized and interconnected world, it becomes difficult to sustain
the idea that moral obligations stop at national boundaries, even if one rejects Singer's
utilitarian reasoning. While Rawls believed that his principles of justice could not be
applied beyond the boundaries of autonomous nation-states [53,61], Beitz argues that this
formulation fails to recognize that the interdependency of modern societies undermines
national autonomy and creates a new basis for justice [62]. Because a state's endowment of
natural resources are contingent—and thus morally arbitrary in a Rawlsian sense—Beitz
contends that “principles of distributive justice must apply in the first instance to the world
as a whole, then derivatively to nation-states” [62] p. 383.

Other approaches focus less on Rawlsian contractualism, but on the conditions for living a dignified life. Shue argues that all human beings are entitled to the protection of certain basic rights, which constitute “everyone’s minimum reasonable demands upon the rest of humanity” [63] p. 19, while Nussbaum instead focuses on human capabilities that are necessary for flourishing (e.g., bodily health and integrity, self-determination, and free expression), to which all human beings are entitled regardless of geographic location [64]. Insofar as locust plagues cause human suffering, deprive individuals their basic rights of subsistence and security, or undermine their ability to flourish, they generate moral obligations to provide aid regardless of political boundaries.

Statists object to such arguments despite their appeal to moral intuitions about uni-
versality and equality. Nagel argues that justice refers specifically to duties shared by
co-citizens, by virtue of living under a common sovereign [65]. His argument is not merely
pragmatic—that without a world government is difficult if not impossible to enforce the
demands of cosmopolitan justice—but that living under a common sovereign who wields
violence in one’s own name creates special ethical bonds among compatriots that give rise
to the demands of justice. While we have basic humanitarian obligations to all people to
alleviate extreme distress, the demands of justice, which concern questions of equality and
political relationships, are properly bounded by political membership. Miller critiques
cosmopolitan theories of justice for imposing uniform sets of rights and duties over and
against the diversity of communities around the world [66]. Cosmopolitanism excludes
“the possibility that there exist deep cultural differences between and among societies
which the members of each find valuable, and which they want to see protected by political
means” [66] p. 84. While these statists may accept that providing humanitarian assistance
in response to locust plagues may be morally good, they would reject that the demands
of justice generate equal responsibilities to victims of distant locust plagues as they do to
those suffering from hunger or poverty within their own political communities.

Eschewing the binary choice between cosmopolitans and statists, we follow theoretical projects that navigate between the extremes of the overwhelming burden of cosmopolitan justice on one hand and the moral isolationism of statist conceptions of justice on the other. Rejecting the logic that the demands that justice must either be restricted to one's own political community or have universal reach, Forst argues that many questions of transnational justice involve multiple overlapping relationships of power, domination, and inequality at local, national, and transnational scales [67]. Shifting perspective from abstract ideals of justice towards actual victims of injustice, "... reveals that theirs is a situation of multiple domination: most often they are dominated by their own (hardly legitimate) governments, elites, or warlords, which in turn are both working together and are (at least partly) dominated by global actors... The various contexts of justice—local, national, international, and global—are connected through the kind of injustice they produce, and a theory of justice must not remain blind to this interconnectedness" [67] (pp. 166–167).

Locust plagues can best be understood as involving multiple contexts of justice—from domestic concerns of failed preventative management and socioeconomic inequalities that leave the vulnerable at greatest risk, to transnational economic and political forces that weaken state capacity to address these compound challenges, to the broader contexts of global climate change and the lasting legacies of colonialism on economic development. Given this complexity, the proper question of justice is not, “Do I have any moral responsibility to assist those suffering from locust plagues?” Instead, in an attempt to lay the foundation for what we hope will be a continuing discourse on moral agency and the just allocation of responsibilities pertaining to locusts, we consider two essential questions: Who are the moral agents that can be held accountable for achieving justice, and how should the responsibilities for reactive and preventive programs be fairly distributed among these agents?

4. Moral Agents in Locust Management

4.1. *Who Is Responsible?*

Individuals are paradigmatic moral agents, having the capacity to understand and respond to ethical obligations. The ability to be morally responsible is often taken as a hallmark of moral personhood, distinguishing human persons from other animals. As Kant writes, "A person is a subject whose action can be imputed to him" [68] p. 16. However, other types of agents are also treated as capable of bearing moral responsibility, including collectives [69], states [70], and international institutions [60]. As O'Neill argues, theories of justice that do not identify which agents are responsible for realizing them are necessarily incomplete and generate considerable theoretical and practical challenges [70]. For example, the Universal Declaration of Humans Rights adopted by the United Nations in 1948 asserts that individuals have certain rights, but fails to specify who has the corresponding duties. The Declaration contends that every individual and "organ of society" should strive to advance human rights, but tacitly identifies states as the primary agents without any explicit rationale.

When considering who should be responsible for reactive and preventive programs for the desert locust, are the proper subjects of moral accountability subsistence farmers, global citizens, rural communities, scientific organizations, local governments, regional governments, ministries of agriculture, afflicted nations, foreign governments, relief organizations, corporations, and international bodies [7,14,30,43]? The result is a cosmopolitan conception of individualized rights enmeshed within a vaguely statist view of moral duties. While an Ethiopian farmer has a right to avoid starvation due to desert locust damage, who is morally obligated to treat the devastating plague is not evident.

One might intuitively contend that whoever is causally responsible for a harm is a moral agent. Indeed, responsibility is often, as Young summarizes, assigned “to a particular agent (or agents) whose actions can be shown to be causally connected to the circumstances
for which responsibility is sought” [71] p. 116. However, causal responsibility is neither necessary nor sufficient for moral responsibility. One can cause harm to another person purely by accident and so accrue no moral responsibility, and one can be obligated to provide aid to a suffering individual without having caused the harm. The desert locust case demonstrates this point: No single agent is uniquely causally responsible for a locust plague, but that does not eliminate all responsibility to provide preventative and reactive aid. We contend that causal contribution is best understood as a factor in allocating responsibility rather than assigning agency. Therefore, we consider two broad approaches to identifying the moral agents responsible for global justice, with particular attention to the management of the desert locust: the capacity-and-capability model and the social connectionist model. Before addressing these, however, a crucial distinction must be made.

Not every assemblage of moral individuals constitutes a new moral agent [60,72]. A mere grouping of people (or collection of social units, such as nations) can be termed “aggregate collectivity,” insofar as the group has no different or greater obligations than the sum of its parts (e.g., the spectators at a sporting event or the countries comprising Asia). This contrasts with “conglomerate collectivity,” in which the assemblage has an identity and continuity over time, organizational and decision-making procedures, and an ability to take purposive action through deliberative goals. Such institutional agents can possess novel or emergent moral responsibilities beyond those of their members, and might be exemplified by the United Nations or the Global Locust Initiative (2020) [73]. It is sometimes useful to also distinguish primary from secondary agents of justice, the former exerting control over the latter (e.g., the UN versus the UNFAO, or the US Congress versus the US Agency for International Development) [70].

## 4.2. *Contemporary Models*

### 4.2.1. Capacity-and-Capability Model

O'Neil contends that institutional or collective agents of justice must possess two features: the capacity to make moral decisions and the capability to affect these decisions [70]. Along these lines, Erskine contends that institutional agents have capacity insofar as they can engage in moral deliberation and thereby take on collective responsibility [60]. For example, the FAO's Desert Locust Control Committee, the government of Kenya, and Dow AgroSciences all have the potential to assess their organization's collective duty to respond to a locust plague. Each of these groups possesses the temporal continuity, analytical processes, and goal-setting mechanisms for conglomerate collectivity.

Capacity is a necessary but insufficient condition of being an agent of justice, as good intentions without commensurate actions might satisfy a deontological standard, but most views of justice require a consequentialist element as well. As such, agents must also possess the capability to actualize the outcome of their moral reasoning—to deploy resources in actual circumstances [74]. In essence, this requirement reflects the ethical principle that “ought implies can”—that to say one should act in some manner entails that the agent has the ability to do so. However, as Caney argues in the context of climate change, there are considerable limitations to ascribing responsibility on the basis of capacity alone, as it ignores how injustices themselves produce inequalities in capacity and can absolve those who have contributed to an injustice if they now lack effective capacity [75].

Additionally, capability is a continuous, rather than discrete, feature of an institutional agent. As Sardo argues, using discrete qualities of agents as criteria for responsibility overlooks the social, economic, and political structures within which agents are embedded and that generate differences in capacity [76]. For example, an agent that has fostered dependency and thereby diminished the capability of another agent may thereby become responsible for either providing resources or developing autonomy and capability in the reliant agent (e.g., a European nation in relation to its former African colony). Therefore, Sardo argues that in the case of complex and compound structural injustices, such as climate change and, as we contend, locust plagues, responsibility should be ascribed on
the basis of social-relational criteria, rather than individualistic ones [76]. One such theory of relational responsibility is Young's "social connections model" [71,77].

### 4.2.2. Social Connection Model

Although cosmopolitan principles of justice would apply to all moral agents, O'Neil raises the concern that ceding the obligation to act on behalf of afflicted people to global institutions could degenerate into a kind of centralized tyranny [70]. One approach to avoiding such a situation would be to disperse the responsibility among a plurality of agents. Such a strategy can be found in Young's critique and reconceptualization of Rawls's understanding of the basic structure of society, in which she makes the case that modern life entails vital, mutual interests extending far beyond the borders of one's nation into a system of international connectivity [71,77].

The social connections model is based on the recognition that people participate in political institutions as a response to individuals being socioeconomically interdependent, and that these connections often arise without regard to political boundaries. According to this view, truly global moral obligations, such as human rights, are not the proper realm of justice, as universals do not arise from, nor are they contingent upon, social relationships. However, all agents who contribute by their actions to economic and political systems that yield unjust distributions of resources among affected countries have a responsibility to remedy these moral failings. This responsibility is different than the standard notion of liability insofar as many current injustices are the product of sociohistorical events giving rise to so-called structural injustices that are immoral in a way that is distinct from the wrongful action of either individuals (who may participate in and benefit from the structures while not having created them or intended harm) or states (which may not willfully diminish the well-being of the repressed people). As such, it is not possible to trace specific actions by a US citizen or the French government, for example, to the suffering of a chronically impoverished Somali farmer during a locust infestation.

The social connections model, therefore, can fruitfully negotiate between the cosmopolitan and statist conceptions of justice and responsibility. It recognizes the realities of economic interdependence without holding individuals responsible for rectifying every injustice everywhere on Earth. In the case of desert locust plagues, it does not blame individuals for the suffering caused by these disasters. However, individuals can be held responsible in a forward-looking sense to act not merely to provide humanitarian aid, but to work to reform the national and transnational institutions that unequally distribute the harm of natural disasters such as locust plagues. This responsibility is not universal, but adheres to those who participate in and benefit from the same structures and institutions that lead to the compound injustice of locust plagues.

### 4.3. Inventory of Moral Agents in Desert Locust Management

Our goal is not to settle theoretical debates between different theories of responsibility, but to draw on both the capacity and capability (C&C) model and the social connections (SC) model to identify responsible agents in the context of pest management. This yields a realistically complex suite of parties given the nature and scope of desert locust infestations.

#### 4.3.1. Multinational Agents

The unspecified "global community" is an aggregate collective lacking the necessary qualities for moral responsibility. In terms of the desert locust, the dominant, conglomerate collective is the UN and its secondary agent, the FAO. This collective, along with its downstream organizations (Regional Commissions, Desert Locust Control Committee, and Emergency Centre for Transboundary Plant Pests) all have substantial capacities and capabilities, as well as elements of social connectivity.
4.3.2. National Agents

At the national level, it is important to consider both strong and weak states. The former unambiguously meet the criteria of the C&C model [70]. The executive and legislative branches of these governments constitute the primary agents, with various development agencies being secondary agents (e.g., the French Agricultural Research Centre for International Development).

The agency of weak states is a matter of degree according to the C&C model. So-
called quasi-states, exemplified by several countries in the Middle East and sub-Saharan
Africa, are exceptionally dependent on foreign creditors and lack institutions to constrain
or outlast the individuals holding power [60]. As such, they exhibit aggregate, more
than conglomerate, collectivity. In comparison, weak states have greater autonomy, al-
though still depending to a substantial degree on international aid, which can impede their
sovereignty [78]. Miller contends that the wellbeing of weak states is largely a function
of external, economic, and historic conditions that would entail the obligation of strong
states via the SC model [79]. A country having habitats that give rise to desert locust
outbreaks is an ecological accident, which might be analogized to a person having a genetic
handicap that entails dependency and hence generates a moral duty for others to provide
accommodations.

4.3.3. Nonstate Agents

There are at least three nonstate agents of justice. First, NGOs of various types have capacity but often limited capabilities, although they actively cultivate social connectivity. Examples of these agents include international aid organizations (e.g., CARE and Mercy Corps) and university-based organizations (e.g., the Global Locust Initiative and Association for Applied Acridology International). Next, corporations meet the criteria of both the C&C and SC models. Although desert locust irruptions are too erratic for the agrichemical industry to bother shaping locust-management policies and markets (producers of locust-specific biological insecticides have a greater interest), their products are important to preventive and reactive programs. Just as it is sociologically simplistic to advance the Rawlsian or “realist” view that states act only in their own self-interest, corporations need not be solely committed to maximizing profits as exemplified by B-corporations and others with social responsibility provisions [70]. And finally, the SC model suggests that citizens of industrialized nations bear some moral responsibility by virtue of their benefiting from structural injustices that disadvantage locust-afflicted people, although it must be recognized that their capability of meaningful action is extremely limited.

**5. Distribution of Responsibilities**

5.1. *Four Standards of Global Justice*

The C&C and SC models allow us to generate an inventory of potentially responsible agents. However, given both the number of agents, at various scales, who have either the capacity to respond or are implicated by social connections, as well as the complexity of the challenge of desert locust management, such an inventory is necessary but insufficient. We also require a framework for distinguishing among these agents and allocating particular duties to particular agents. Neither the C&C nor the SC model accomplishes this in isolation. As the proponent of the latter model, Young identifies “parameters of reasoning” that can be used to allocate specific duties, including capacity, privilege, interest, and ability [71] (pp. 144–147). However, to better operationalize the standards for fairly distributing the responsibilities for preventative and reactive locust management, we turn to Miller’s more perspicuous analysis, which applies to agents ranging from individuals to conglomerate collectives (international organizations, nations, corporations, etc.) [79]. This model provides four concrete standards for allocating responsibility: causal, moral, capacity, and community.
### 5.1.1. Causal Responsibility

That moral agents who cause harm to others bear a commensurate responsibility to correct the wrong is a commonsense moral intuition. However, as we have argued previously, causal responsibility is neither necessary nor sufficient to generate corresponding moral and political responsibilities, especially in cases of compound and structural injustices. Miller's principle of causal attribution can still be useful in distributing responsibilities to the responsible agents identified by the C&C or SC models of responsibility [79], especially when modified as Shue's (1999 [80] p. 534) "greater contribution principle," which does not imply that the responsible agent is the exclusive cause [80] p. 534. Of the agents who have the capacity to respond to locust plagues or participate and benefit from the global political-economic structures that leave some states more vulnerable to and unable to effectively manage locust plagues, greater burdens should be placed on those who have contributed more to the problem.

Applying causal responsibility to the case of locusts can be challenging, given that swarms (the proximate cause of human suffering) are not moral agents, while the contribution of moral agents—whether individuals, states, or international institutions—are indirect and mediated. However, as Sardo analogously argues, the proper object of responsibility for the structural injustice of climate change is not discrete greenhouse-gas emissions, but the global political-economic structures that both intensify fossil-fuel extraction and unevenly distribute the benefits of such vulnerability and the risks of climate-related hazards [76]. In the case of locust plagues, climate change is aggravating the unpredictability and severity of plagues [35,36]. As such, the industrialized nations with disproportionate CO₂ emissions bear a commensurate, if partial, responsibility for the consequences of erratic and severe weather with regard to pest population dynamics. Additionally, colonial powers played a major role in creating weak governments, unstable societies, aggressive militaries, and dependent economies in their former colonies—all of which undermine both implementing preventive strategies and mounting reactive programs during upsurges and plagues. In an important sense, this complex network of causal responsibility involving locust plagues, climate change, and economic inequality might be best understood as constituting a global, structural injustice. Therefore, the idea of contribution should be expanded to include these climatic, geopolitical, and historical forces that unevenly distribute vulnerability and adaptive capacity for locust plagues.

### 5.1.2. Moral Responsibility

If an agent's harm is foreseeable, intentional, and unjustified (again, inequities can arise through legitimate processes), there is moral culpability—even without causal responsibility. For example, failure to monitor a risky situation could constitute wrongful neglect [79]. In an international context, even excusable ignorance of how injustices arose does not obviate moral responsibility [81]. In fact, Vanderheiden argues not only that ignorance is not exculpatory, but that agents have a positive responsibility to educate themselves to a reasonable degree about predictable natural disasters and other hazards [82]. What matters is synchronic features (present considerations of an agent's obligations to those who are suffering, limited by the agent's ability to render aid and to bear sacrifice), rather than diachronic considerations (how the suffering came to be). Miller argues that while an agent may have a synchronic moral duty, having participated in the genesis of a harm also can entail moral responsibility [79]. Hence, causal responsibility can engender moral responsibility, but it is not a necessary condition.

Therefore, greater burdens should be assigned to those agents in positions of relative power who foresaw, or should have foreseen, the hazards of locust plagues, but failed to take the necessary preventative action. This would place greater burdens on states and institutional agents than on individuals. Although countries with causal responsibility might have a greater duty to act, standing by while afflicted farmers or pastoralists suffer is not morally defensible even for those countries without a clear diachronic role in the crisis, when taking action could mitigate the harm suffered. Adapting the line of argument
provided by Caney [81], our options are to: ascribe mitigation responsibilities to the subsistence agriculturalists, do nothing and thereby allow serious harm, or ascribe duties to more powerful agents. The third option seems the only practical and principled course of action. However, we must keep in mind that “ought implies can” in formulating moral duties, so the pragmatic element of Caney’s third option leads to the next standard with respect to global justice.

### 5.1.3. Capacity to Act

This principle states that those agents with the greatest power to remediate suffering are obligated to do so. In an international context, Miller contends that those with the most resources are expected to shoulder a greater proportion of the burden, a duty that amounts to a kind of progressive taxation [79]. An objection to this standard is that the expectation would be a disincentive for wealthy nations to continue their financially successful practices if doing obligates them to ever greater contributions to poor nations. Miller replies that indefinite growth of production and consumption are not sustainable, regardless of whether global justice requires increased contributions [79]. Moreover, there is no evidence that economic growth depends on unlimited incentives. Another concern is that the synchronic nature of capacity does not require that we consider how an injustice or crisis arose. However, capacity also does not preclude considering causal responsibility.

The application of the capacity principle to locust management is rather straightforward: Wealthier nations are morally obliged to provide greater financial assistance to support both preventative and reactive measures in response to locust plagues. However, it should be noted that money is not the only resource relevant to capacity. Some industrialized nations have greater, relevant scientific and technical expertise. Nor should we focus entirely on nations, as substantial capacity can also be found in universities (e.g., scientific and technical expertise) and corporations (e.g., insecticides, application equipment, and safety supplies). Although we cannot expect a company to donate materials, businesses have a moral obligation to sell their products without profiteering. It should be noted that the capacity to intervene during a plague might be different than that needed to develop and sustain preventive programs. Given the economic efficiency of prevention, an agent’s capacity is greatly enhanced by contributing to preventive management. Some might object that capacity is an unrealistic standard in the absence of a sociopolitical relationship between donor and recipient. This brings us to the final principle of global justice.

### 5.1.4. Communal Responsibility

As our discussion of the scope of global justice suggests, social relationships are morally relevant with regard to the allocation of duties pertaining to global justice. Miller contends that a communitarian principle that recognizes special ties accords with our moral intuitions [79]. For example, we accept, ceteris paribus, that duties to friends are greater than to strangers. If Young’s social connections successfully makes the case that responsibility for harm derives from structural injustice, then it follows that an agent’s responsibility to provide aid would likewise track structural or communal linkages [77]. However, reducing connections, and hence obligations, to the level of individuals becomes morally impotent given a person’s very limited ability to influence structural injustice within the international community (recall that “ought implies can”). The problem with an individualistic approach can be avoided by considering communal relations that exist among conglomerated agents. Nations, agencies, NGOs, and corporations may have particular relations with afflicted countries that entail ethical responsibilities.

With regard to locust management, countries sharing common languages, religions, and cultural practices may often be wealthy nations and their former colonies. Importantly, past relationships of unjust domination created international communities and hence particular moral duties—not by virtue of remediating historical wrongs (although this is relevant to causal responsibility), but by virtue of contemporary connections. So, European nations have particular obligations to their former African and Asian colonies that are
afflicted by locusts. In addition, international communities such as the FAO's Regional Commissions for Locust Control generate mutual obligations. When member countries fail to pay their annual dues and the organizations are consequently unable to conduct preventive programs [14], the resulting upsurges and plagues reflect an injustice and moral culpability within these regions. And finally, NGOs, religious denominations, universities, scientific organizations (e.g., the Orthopterists Society, which is an international group devoted to the study of grasshoppers, locusts, and their relatives), and other conglomerate collectives may have communal responsibilities through relationships to locust-afflicted countries, districts, or even villages.

## 5.2. Resolving the Standards

The principles guiding the just allocation of responsibilities among moral agents might be complementary in some cases (e.g., causal responsibility may align with moral responsibility, or causal responsibility may track communal responsibility). However, the principles may often be conflicting (e.g., an agent with the greatest capacity to act may have no causal responsibility) or unrelated (e.g., being agents within a community has no necessary relationship to those agents having the capacity to act). As such, how to integrate the four standards of global justice is a challenge for which there are at least four possible approaches [79].

### 5.2.1. Particularism

Few, if any, real-world cases will reduce to a single standard (e.g., a situation with capacity and no elements of causal, moral, or communal responsibility). On the other hand, there is no obvious formula for balancing the four principles, so we might abandon the search for a universal theory and simply deal with every case on its own terms. However, this ad hoc approach provides no guidance as to how the factors should be integrated in a consistent and rational matter.

### 5.2.2. Master Principle

We might attempt to defend one of the principles and set aside the others. However, arguing for a single consideration seems doomed, as there are sound reasons for each of the standards, and choosing any one of them could result in either solely backward-looking considerations, as with causal responsibility, or forward-looking considerations, as with moral responsibility. The choice of a master principle might also give rise to situations in which nobody would be obligated to help (e.g., an earthquake with the master principle of causal responsibility). There also are surely cases in which justice demands more than a single factor (e.g., a community of nations with radically unequal capacities).

### 5.2.3. Integration

The standards of global justice could be integrated in two ways. First, the principles could be applied in series (e.g., first moral responsibility, then causal, then communal, then capacity). However, the problem is that in any series, the initial standard will be a matter of degree, and in some cases a lower-order principle might well warrant greater consideration. Moreover, it is not clear how a sequential process would take into account conflicts among the principles (e.g., would there be a simple, ordinal weighting?).

The other integrative approach would be openly pluralistic, applying the principles in parallel. Such a simultaneous methodology would risk degrading into particularism, as there would be no overarching strategy. So, we might propose a heuristic such that immediate suffering is considered first (e.g., hunger from a locust plague) along with the most relevant standards (e.g., morality and capacity), followed by mitigating long-term problems arising from injustice (e.g., preventive programs for locust management) with their relevant standards (e.g., community and causal). However, as stated, even this approach would become idiosyncratic when applied to the complexity of international crises.
5.2.4. Connectivity

Perhaps the most operationally viable approach to finding an optimum between a
formulaic integration with a strict “decision rule” and a vague particularism with the risks
of ad hoc rationalization is a kind of dynamic compromise providing structural guidance
to a pluralistic integration of the standards for global justice. Miller proposes a strategy
of applying the principles according to their relative strength of connection to each of the
agents [79]. For example, one agent may have a particularly strong causal responsibility,
while another might have a highly developed communal obligation, and a third could
have a great deal of capacity. Each then would be obligated to act in accordance with its
connectivity, assuring that some agent can be held morally accountable and avoiding the
problem of the agents waiting for others to act or debating who has the greatest duty. As
such, international responsibility is divided among the agents such that they acknowledge
connections to the afflicted people that compel action, rather than rationalizing which
of the standards are inapplicable and thereby offering excuses for avoiding involvement.
The result of connectivity theory is a kind of internal complexity with significant, if not
formulaic, clarity—a situation that would appear to mirror real-world cases. Miller points
out that this strategy does not preclude sensible ordering of standards reflecting the nature
of the problem being addressed. For example, during a humanitarian crisis, capacity may
be the highest priority—and whichever agent has the strongest connection to this standard
would be compelled to act.

6. Applications to Locust-Management Scenarios

In the following scenarios of desert locust management, we construct simulations using plausible but necessarily idealized moral agents and sociopolitical relationships We considered using actual cases from the last few decades of locust management, but many of the potentially relevant details were not documented, and to generate a tractable analysis within the constraints of this paper, we would be compelled to ignore many of the nuances, organizational layers, and competing demands that were part of the record. Moreover, rather than assigning retrospective blame for past shortcomings, our goal is to illustrate the operationalization of the four principles of global justice using Miller’s model of connectivity using realistic, if simplified, conditions [79].

6.1. *Scenario 1: A Desert Locust Plague (Reactive Programs)*

6.1.1. Scenario

There is a serious invasion of locust swarms during a plague into country X from distant sources in countries Y and Z. All three countries are impoverished with nominal export economies. There are many subsistence farmers in X, a country with a weak government involved in long-term conflicts with Y and civil unrest within its own borders. These military actions have been conducted in political alliance with wealthy country A whose interests align with country X, which is a former colony, while wealthy country B has supported the militaries of countries Y and Z. Country X has provided funding to the regional locust commission (R) that includes its neighbors, but tensions with countries Y and Z have impeded cooperation in terms of developing a strong outbreak-prevention program. All five of the countries (A, B, X, Y, and Z) are members of an international organization that was formed to provide crisis and development assistance on a global basis and whose director (I) determines the funding and logistical support allocated to the regional commission (R). An international NGO (N) is reluctantly accepted by the government of country X, but its work is appreciated by the local people who value the efforts to provide agricultural support and food relief to rural villages.

6.1.2. Analysis

There is an urgent need for assistance in country X to avoid crop loss by subsistence
farmers who will suffer hunger and/or loss of land in the short term and perhaps health
and education detriments in the long term.
With regard to **causal** responsibility, the swarms originated in countries Y and Z, so their ecosystems are the proximate cause of the swarms in country X. However, only to the extent that the governments of countries Y and Z failed in their duties to guard against outbreaks given available resources, would they have moral (ultimate) responsibility. When considering causal responsibility in terms of contribution rather than exclusive causality, more agents bear responsibilities. The political meddling of countries A and B constitute important, if less-immediate, causes of the situation by having impeded the development of preventive approaches in the region through organization R with support approved by director I. In historical terms, country X was a colony of country A, and this legacy accounts for a continuing lack of internal political capacity. Organization N has done nothing to cause the locust plague.

As for **moral** responsibility, the government of country X has a duty to provide for its citizens. The other countries (A, B, Y, and Z) have a common, humanitarian obligation to the suffering of those in country X. Organization R has no special, moral obligation, but the director (I) has the individual duty to fulfill the charter of the organization to aid nations in peril. Organization N has raised its operating funds through an explicit commitment to relieving hunger.

In terms of **capacity**, countries A and B have the resources needed to mitigate the immanent suffering, while countries X, Y, and Z are without the financial or logistical means to fully address a locust plague. The resources from countries A and B could be provided bilaterally to country X, but director I oversees an organization constructed to receive and distribute funds to needy people, including through commission R. Organization N is overwhelmed by the demand for food in locust-afflicted villages.

Country X is in a geopolitical **community** relationship with its neighbors (mere physical proximity would not constitute a community, although bordering countries typically establish international agreements). All three countries belong to the same regional locust commission (R), although this association is undermined by political hostilities. The colonial history and political bonds form a strong communal relationship between countries X and A. All of the countries belong to the international global community for which director I has responsibility. The director's obligations are diluted by virtue of its expansive membership. Organization N is begrudgingly present in the eyes of country X's government, although its work is valued locally.

In summary, given the urgency of the situation, the moral principles might be ordered such that capacity > community > moral = causal. Then, considering the evident strength of connections among the moral agents, the result would be one in which the responsibility for relieving the human suffering falls very strongly on country A and somewhat less on both country B and the director (I) of the international organization. Still less and relatively equal moral responsibility would accrue to countries X, Y, and Z, as well as organizations R and N.

## 6.2. Scenario 2: Desert Locust Recession (Preventive Programs)

### 6.2.1. Scenario

During a recession period, countries U, V, and W comprise a regional commission (organization R) charged with developing outbreak-prevention programs with the support of an international organization (I). While all three countries are impoverished, U and V have functional governments, while W is wracked with corruption by an authoritarian government. Countries U and V share a colonial history with country C, a wealthy nation. Country W has an abundance of oil, but most of the profits flow to the world's largest energy company (E, with stockholder, e) headquartered and taxed in country D, a wealthy nation. Historically, country U has few locust breeding sites; country V has many such habitats, but landmines (provided by country C during hostilities a decade earlier) make access dangerous; country W also has many breeding sites, but very poor roads. Models generated by organization I predict imminent shifts in rainfall patterns as a consequence of climate change attributable to a group of industrialized countries (G, which includes
C and D). These precipitation patterns will expand breeding habitats in country U and foster those in V and W. An international nongovernmental organization (N) pursues agricultural-development projects in the region, but lacks expertise in locust management.

6.2.2. Analysis

A viable preventive program in the region (R) requires the cooperation of countries U, V, and W. However, these agents cannot sustain such a program in light of their depleted economies and competing demands for healthcare, clean water, rural education, etc.

In terms of **causal** responsibility, a failure of prevention could be attributed to the relevant countries (U, V, and W) and the regional organization (R). However, the poverty of these agents can be traced to the colonialism of country C (along with the landmines making access dangerous) and the exploitation of natural resources by company E, which in turn benefits both its stockholder e and country D. The international organization (I) is limited by the funds provided by member nations. The intensification and expansion of locust breeding areas is assignable to those countries, G, responsible for emitting the greatest share of greenhouse gases.

With regard to moral responsibility, the prevention of a humanitarian disaster by a locust plague is arguably most heavily assigned to the international organization (I), given their mandate. In light of the benefits that have accrued to wealthy nations C and D through colonialism and continuing extraction of resources, these agents bear substantial responsibility. A similar case could be made for company E, although the direct linkage to locust-afflicted nations is somewhat weaker, and the connectivity of its stockholder (e) is much less but nonzero. The governments of U, V, and W also have some responsibility to their own people as well as those in the larger area, but their ethical burden is mitigated by poverty (particularly country W, given its weak government). This reasoning also applies to the regional commission R, although this organization has a much narrower duty than the affiliated countries and receives support from organization I. Finally, the NGO has no relevant expertise in locust management and no obligations to do that which is outside of its ability ("ought implies can").

Turning to **capacity**, regional organization (R) and the wealthy countries (C, D, and the collective, G) bear the greatest burden. International organization I has a multiplicity of responsibilities, only one of which is prevention of locust plagues. The impoverished countries (U, V, and W) have broad obligations and limited resources, as does the nongovernmental organization N, while country W further lacks the political ability to contribute. The energy company (E) has assets needed for a preventive program and a duty to provide these while meeting fiduciary obligations to its shareholders, including e, whose capacity is vanishingly small.

And finally, considering **community**, countries U, V, and W form an association geographically and through their collective support of organization R, which represents the locust-management community. There is a strong communal component of country C with countries U and V by virtue of historical relations. Country W's government makes for a weaker communal ability, although it has an economic relationship with company E, while stockholder e participates in the corporate community. Both E and e therefore have an economic connection to country D. The nongovernmental organization (N) has a strong relationship with countries U and V, but lesser so with country W. Both the international organization (I) and the industrialized countries (G) are weak elements of a community concerned with locust outbreak prevention by virtue of diverse global connections.

In summary, given the chronic, rather than acute, nature of this case, the moral principles might be ordered such that causal > moral > community > capacity. Then, taking into account the evident strength of connectivities among the moral agents, the result would be that the greatest obligations to prevent the harm resulting from a locust plague accrue at the country level, including the wealthy (C and D) and impoverished (U and V) nations. The responsibilities of the former arise in consideration of their moral duties and the latter in consideration of their causal efficacies. Of the organizations, only the
regional commission (R) has a high obligation, while the larger collectives (G and I) and the company (E) have moderate obligations, largely due to weaker communal and causal considerations (even less for stockholder e). Likewise, country W has moderate obligations in consideration of its weak government, which undermines capacity and community. The nongovernmental organization (N) has high moral and communal factors, but no causal responsibility or capacity, so its overall obligation is low.

### 6.3. *Summary*

In both scenarios (preventive and reactive), moral responsibility primarily falls to wealthy countries. However, in the preventive scenario, the allocations are more evenly distributed among countries, and the international and regional organizations bear a greater burden than in the reactive scenario. In the reactive case, the wealthy countries clearly have the greatest responsibility, which reflects the weight put on capacity during a crisis (of course, funds may pass through the international organization).

The allocation of responsibilities for global justice in these cases does not diverge markedly from what we would take to be common, moral intuitions in which causal responsibility and capacity would seem to be important considerations and wealthy countries are thought to bear the greatest burden. Rather, the advantage of adapting and applying Miller's fourfold principles along with network theory is that we have an explicit set of reasons for our ethical inclinations rather than merely doing what "seems right" without being able to explain or defend our decisions to those who fail to share our intuitions [79]. In short, it is desirable to do the right thing, but it is far more intellectually and morally valuable to do the right thing for the right reasons.

That said, we do not possess anything approaching certainty through some sort of moral mathematics. This analysis does not yield artificially precise quantitative results that might be generated by converting the various factors into numerical values for a spreadsheet. As much as such exactitude would seem desirable, it would substitute easy answers for the hard work of democratic deliberation. So, the framework provides a means by which individuals and communities can think through the nature of their responsibilities in the course of negotiating a just approach to developing both preventive programs of locust management and reactive responses during upsurges that may become plagues.

Perhaps even more importantly, with a conceptual formalization, we now have a method for critically analyzing novel cases of locust management that are likely to emerge given rapidly changing political, economic, and environmental conditions. Unfamiliar conditions may reduce the relevancy of our experiences and lead to conflicting moral intuitions. As new situations arise, having a theoretical framework for identifying moral agents and distributing responsibilities to achieve global justice will be important.

## 7. *Conclusions*

Our purpose in this paper was to address the rising awareness in the field of locust management that the limiting factor in making substantive progress has become a serious consideration, as well as integration of the social sciences and humanities with the natural sciences [7,21,83]. Oftentimes, we know what strategy and methods to implement from entomological and ecological perspectives to improve the efficacy of management, and so the obstacles are not more or better data about the insects, although greater knowledge is surely an asset, and we would not discourage continued research on locust biology with important implications for sound pest management (e.g., [84]). Rather, the impediments are economic, political, and cultural understanding. As such, we sought to sketch an approach to making socially and ethically sound decisions about desert locust management through the framework of global justice, informed by conventional moral theories. Two findings emerged from our analysis, perhaps neither of which is terribly surprising to those in the field.

First, there is a tremendous diversity of moral agents, including individuals, scientific organizations, nongovernmental organizations, corporations, nations, government
agencies, regional commissions, and international bodies. If anything, our analysis likely
expanded the inventory of collective, moral agents while providing a sound rationale
for inclusion.

Second, justly allocating responsibilities among the agents during a preventive or
reactive program of locust management is a complex task. However, there are intellectually
compelling principles to provide at least a working model for how these duties ought to be
distributed. While natural scientists might be understandably frustrated by the imprecision
of our framework, we would point out Aristotle's admonition:

> For it belongs to an educated person to seek out precision in each genus to the extent that the nature of the matter allows: to accept persuasive speech from a skilled mathematician appears comparable to demanding demonstrations from a skilled rhetorician. [85] (pp. 3–4)

While a formula for assigning responsibility is not a sensible endpoint, having the
criteria for moral agency, an explicit set of principles, and a plausible, if inexact, theory
for justly distributing the burdens of locust management hopefully constitutes a valuable
starting point for further research and discourse. Our foray into the nexus of locust manage-
ment, social science, and humanities represents a step in working toward a philosophically
coherent, scientifically sound, conceptually defensible, and operationally viable method.

While our discussion of justice has an anthropocentric focus, it should be noted
that many theorists of global justice have argued for expanding the boundaries of justice
beyond species membership in addition to political membership. Singer, for example,
argues that because all sentient creatures experience pleasure and pain, they are also
deserving of moral consideration [86]. Nussbaum also extends her capabilities approach to
ground interspecies justice, based on the idea that nonhuman animals are capable of living
dignified and flourishing lives, with corresponding needs to promote such flourishing [87].
Schlosberg focuses this approach to the level of the ecosystem, rather than the individual or
species, noting that harm to nonhuman animals, in recognition that individual creatures are
harmed by habitat disruption and destruction and that ecosystem integrity and functioning
contribute to human and nonhuman flourishing [88].

Although a detailed engagement with questions of interspecies justice is beyond the
scope of this paper, these arguments raise important questions in the context of locust
swarms that demand further interdisciplinary research. Insofar as locust swarms and
their management disrupt the integrity and functioning of ecosystems, they may generate
obligations of justice on behalf of those ecosystems, especially when such disruptions are
caused by anthropogenic climate change. Furthermore, management strategies should be
sensitive to ecosystem functioning and integrity, and the long-term ecological consequences
must be considered when evaluating the justice of both preventive and reactive strategies.
Finally, the moral framework we have proposed does not solve the political problem of
actually getting agents (especially powerful states) to bear their responsibilities with regard
to locust management. That is a topic for another line of research that must incorporate
scholarship in political theory, including Schiff's work on how different ways of narrating
injustices can affect how agents acknowledge and act upon their responsibilities [89], and
Ackerly's human-rights model of responsibility, which identifies principles-in-practice
for agents to leverage their existing social roles and relationships to discharge their re-
sponsibilities for combatting injustice [90]. Our goal is that, having opened up space for
dialogue between natural scientific research on desert locust management and political
and moral philosophies of global justice, future scholarship can engage the questions our
analysis generates.

**Author Contributions:** Conceptualization, J.A.L. and M.C.S.; methodology, J.A.L. and M.C.S.; formal analysis, J.A.L. and M.C.S.; writing—original draft preparation, J.A.L.; writing—review and editing, M.C.S.; investigation, J.A.L. and M.C.S. Both authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.