Global Aerial Habitat Conservation Post-COVID-19 Anthropause
Authors: Santiago Zuluaga, Karina Speziale, Sergio A. Lambertucci
Journal: Trends in Ecology & Evolution (2021)

Aerial habitat is increasingly threatened. The coronavirus disease 2019 (COVID-19) anthropause shows that a decrease in human mobility and goods production for even a short period reduces the global anthropogenic impact on airspace fragmentation and pollution. Economic and environmental post-COVID-19 agendas should consider the changes observed in the aerial habitat during the anthropause. Aerial habitat is increasingly threatened. The coronavirus disease 2019 (COVID-19) anthropause shows that a decrease in human mobility and goods production for even a short period reduces the global anthropogenic impact on airspace fragmentation and pollution. Economic and environmental post-COVID-19 agendas should consider the changes observed in the aerial habitat during the anthropause. Aerial habitats are becoming increasingly fragmented [e.g., by skyscrapers, communication towers, power lines, wind farms, aircraft, and unmanned aerial vehicles (UAVs)] and polluted (e.g., by contaminants, noise, and light) [1.Voigt C.C. et al.Conservation strategies for bats flying at high altitudes.Bioscience. 2018; 68: 427-435Crossref Scopus (23) Google Scholar, 2.Lambertucci S.A. et al.Human-wildlife conflicts in a crowded airspace.Science. 2015; 348: 502-504Crossref PubMed Scopus (58) Google Scholar, 3.Davy C.M. et al.Aeroconservation for the fragmented skies.Conserv. Lett. 2017; 10: 773-780Crossref Scopus (46) Google Scholar, 4.Van Doren B.M. et al.High-intensity urban light installation dramatically alters nocturnal bird migration.Proc. Natl. Acad. Sci. U. S. A. 2017; 114: 11175-11180Crossref PubMed Scopus (190) Google Scholar, 5.Diehl R.H. The airspace is habitat.Trends Ecol. Evol. 2013; 28: 377-379Abstract Full Text Full Text PDF PubMed Scopus (84) Google Scholar]. Under this scenario, the global lockdown due to the COVID-19 pandemic has represented a remarkable and unique experiment, recently named 'anthropause' (see Glossary). The pronounced reduction in human mobility and goods production, and particularly the decrease in fossil fuel use over even a short period, have reduced the impact of human activities on the airspace (e.g., aerial fragmentation and aerial pollution). Although the short-term positive effects of the anthropause on aerial habitats have been well documented [6.Gillingham K.T. et al.The short-run and long-run effects of Covid-19 on energy and the environment.Joule. 2020; 4: 1337-1341Abstract Full Text Full Text PDF PubMed Scopus (160) Google Scholar], a post-COVID-19 back-to-normal strategy (business as usual) that favors economic recovery could rapidly override them. If we seek to achieve global biodiversity conservation goals and reduce the effects of climate change at the same time as promoting economic recovery, post-COVID-19 economic and environmental agendas must be developed in tandem and we can take advantage of the changes observed in the aerial habitat during the COVID-19 anthropause. Aerial habitat protection requires synergy between science, government policy, industry, and law for the implementation of aeroconservation measures. Anthropogenic changes in habitat configuration may have different impacts on terrestrial and aerial wildlife species, affecting Nature's Contributions to People (NCP)i. Terrestrial habitat fragmentation greatly impacts the movements of nonflying terrestrial animals [7.Tucker M.A. et al.Moving in the Anthropocene: global reductions in terrestrial mammalian movements.Science. 2018; 359: 466-469Crossref PubMed Scopus (719) Google Scholar]. By contrast, given their capacity for mobility, aerial species, including birds, bats, and insects, may partially overcome terrestrial fragmentation. Nevertheless, terrestrial habitat fragmentation often forces birds and bats to fly longer distances during foraging bouts [1.Voigt C.C. et al.Conservation strategies for bats flying at high altitudes.Bioscience. 2018; 68: 427-435Crossref Scopus (23) Google Scholar,8.Tucker M.A. et al.Large birds travel farther in homogeneous environments.Glob. Ecol. Biogeogr. 2019; 28: 576-587Crossref Scopus (37) Google Scholar]. Together with terrestrial wildlife, many aerial insects, mammal species (like bats), and most birds provide pollination, seed dispersal, disease spread control, carrion removal, and other services [9.Dirzo R. et al.Defaunation in the Anthropocene.Science. 2014; 345: 401-406Crossref PubMed Scopus (2588) Google Scholar] that are essential for human beings. The provision of NCP by terrestrial species has already been reduced due to the high anthropogenic impact on terrestrial ecosystems [7.Tucker M.A. et al.Moving in the Anthropocene: global reductions in terrestrial mammalian movements.Science. 2018; 359: 466-469Crossref PubMed Scopus (719) Google Scholar]. Therefore, the responses of flying animals to changes in habitat configuration may be key for the maintenance of several important long-distance NCP [1.Voigt C.C. et al.Conservation strategies for bats flying at high altitudes.Bioscience. 2018; 68: 427-435Crossref Scopus (23) Google Scholar,8.Tucker M.A. et al.Large birds travel farther in homogeneous environments.Glob. Ecol. Biogeogr. 2019; 28: 576-587Crossref Scopus (37) Google Scholar,10.Lambertucci S.A. Speziale K.L. Need for global conservation assessments and frameworks to include airspace habitat.Conserv. Biol. 2020; (Published online September 25, 2020. https://doi.org/10.1111/cobi.13641)Crossref PubMed Scopus (8) Google Scholar] that terrestrial species are failing to provide [7.Tucker M.A. et al.Moving in the Anthropocene: global reductions in terrestrial mammalian movements.Science. 2018; 359: 466-469Crossref PubMed Scopus (719) Google Scholar,9.Dirzo R. et al.Defaunation in the Anthropocene.Science. 2014; 345: 401-406Crossref PubMed Scopus (2588) Google Scholar]. However, the population decrease in aerial fauna produced by anthropogenic activities [11.Liang Y. et al.Conservation cobenefits from air pollution regulation: Evidence from birds.Proc. Natl. Acad. Sci. U. S. A. 2020; 117: 30900-30906Crossref PubMed Scopus (24) Google Scholar] may have profound effects on ecological processes and NCP, leading to cascading negative effects on ecosystem function and human health and well-being [9.Dirzo R. et al.Defaunation in the Anthropocene.Science. 2014; 345: 401-406Crossref PubMed Scopus (2588) Google Scholar]. Global change drivers currently favor aerial defaunation trends. Long-term surveys have already revealed a net loss in total abundance of 2.9 billion birds across all biomes of North America (abundance reduction of 29% since 1970) [12.Rosenberg K.V. et al.Decline of the North American avifauna.Science. 2019; 366: 120-124Crossref PubMed Scopus (1060) Google Scholar] and a global decline in butterfly and moth populations (reduction in abundance of 40% over 40 years) [9.Dirzo R. et al.Defaunation in the Anthropocene.Science. 2014; 345: 401-406Crossref PubMed Scopus (2588) Google Scholar]. The best-known impacts occur in basoaerial habitats. They include direct physical harm like collisions (e.g., those produced by mobile and stationary structures [2.Lambertucci S.A. et al.Human-wildlife conflicts in a crowded airspace.Science. 2015; 348: 502-504Crossref PubMed Scopus (58) Google Scholar]) and indirect impacts such as the displacement of individuals to lower-quality habitats or the decrease in fitness of aerial wildlife [11.Liang Y. et al.Conservation cobenefits from air pollution regulation: Evidence from birds.Proc. Natl. Acad. Sci. U. S. A. 2020; 117: 30900-30906Crossref PubMed Scopus (24) Google Scholar,13.Senzaki M. et al.Sensory pollutants alter bird phenology and fitness across a continent.Nature. 2020; 587: 605-609Crossref PubMed Scopus (94) Google Scholar]. Industrial contaminants that provoke air pollution (e.g., sulfur dioxide, fluoride, ash, and photochemical oxidants in smog) have also had a negative effect on aerial wildlife worldwide since the industrial revolution (e.g., industrial-related injuries and diseases, physiological stress, bioaccumulation, and direct mortality) [11.Liang Y. et al.Conservation cobenefits from air pollution regulation: Evidence from birds.Proc. Natl. Acad. Sci. U. S. A. 2020; 117: 30900-30906Crossref PubMed Scopus (24) Google Scholar,14.Newman J.R. Effects of industrial air pollution on wildlife.Biol. Conserv. 1979; 15: 181-190Crossref Scopus (41) Google Scholar]. The recent increase in UAVs and the potential arrival of flying carsii could speed up aerial defaunation, mainly by reducing aerial habitat connectivity and increasing disturbances and direct physical harm, such as that caused by collisions [2.Lambertucci S.A. et al.Human-wildlife conflicts in a crowded airspace.Science. 2015; 348: 502-504Crossref PubMed Scopus (58) Google Scholar,3.Davy C.M. et al.Aeroconservation for the fragmented skies.Conserv. Lett. 2017; 10: 773-780Crossref Scopus (46) Google Scholar]. The same effect could be brought about by the synergy between climate change and fragmentation that provoked the death of migratory songbirds in the USA. The combination of unusual climatic conditions most probably lead to starvation and disorientation, thus causing birds in poor health to fly into objects and buildingsiii. The increasing anthropic impacts of fragmentation, climate change, and pollution on the aerial habitat are inevitably associated with an increase in the rate of aerial wildlife losses [11.Liang Y. et al.Conservation cobenefits from air pollution regulation: Evidence from birds.Proc. Natl. Acad. Sci. U. S. A. 2020; 117: 30900-30906Crossref PubMed Scopus (24) Google Scholar, 12.Rosenberg K.V. et al.Decline of the North American avifauna.Science. 2019; 366: 120-124Crossref PubMed Scopus (1060) Google Scholar, 13.Senzaki M. et al.Sensory pollutants alter bird phenology and fitness across a continent.Nature. 2020; 587: 605-609Crossref PubMed Scopus (94) Google Scholar, 14.Newman J.R. Effects of industrial air pollution on wildlife.Biol. Conserv. 1979; 15: 181-190Crossref Scopus (41) Google Scholar]. The economic crisis resulting from the drop in economic activity during the anthropause also produced a short-term positive balance for the aerial habitat. During the initial period of restrictions due to the COVID-19 pandemic, mobility declined to an extraordinarily low leveliv. Road transport in regions under lockdown dropped between 50 and 75%, global average road transport activity fell by almost 50%, and flights decreased by more than 90% in some countries. Given that mobility consumes 57% of the global oil demand, the decrease in CO2 emissions in 2020 (~30.6 Gigatons versus 33.2 Gigatons in 2019) is around two times greater than all previous decreases since the end of World War II combined. It is also in line with the 'Nationally Determined Contribution' targets under the Paris Climate Agreement set for 2025 [6.Gillingham K.T. et al.The short-run and long-run effects of Covid-19 on energy and the environment.Joule. 2020; 4: 1337-1341Abstract Full Text Full Text PDF PubMed Scopus (160) Google Scholar]. These and other reductions in energy demand (i.e., gas and coal) also favored a reduction in other air pollutant emissions, reducing their impact on human [6.Gillingham K.T. et al.The short-run and long-run effects of Covid-19 on energy and the environment.Joule. 2020; 4: 1337-1341Abstract Full Text Full Text PDF PubMed Scopus (160) Google Scholar] and wildlife health [11.Liang Y. et al.Conservation cobenefits from air pollution regulation: Evidence from birds.Proc. Natl. Acad. Sci. U. S. A. 2020; 117: 30900-30906Crossref PubMed Scopus (24) Google Scholar]. These short-term reductions in aerial fragmentation (e.g., aerial traffic), greenhouse gases (e.g., CO2, CH4, N2O), and aerial pollutants [e.g., artificial light at night (ALAN), noise, ozone precursors, particulate matter] during lockdown has had short-term positive effects on aerial wildlife. For instance, a 10-week lockdown in the USA (between March 25 and June 7, 2020) led to a 61% decrease in the number of aerial wildlife strikes (from 3554 to 1386) compared with the same period in 2019v. A reduction in noise pollution levels in urban areas has led to songbirds producing higher performance songs at lower amplitudes, maximizing communication distance and salience [15.Derryberry E.P. et al.Singing in a silent spring: birds respond to a half-century soundscape reversion during the COVID-19 shutdown.Science. 2020; 370: 575-579Crossref PubMed Google Scholar]. These reductions in the impacts of global change drivers around the world have probably had a positive effect on the quality of aerial habitats for invertebrates, birds, and bats [11.Liang Y. et al.Conservation cobenefits from air pollution regulation: Evidence from birds.Proc. Natl. Acad. Sci. U. S. A. 2020; 117: 30900-30906Crossref PubMed Scopus (24) Google Scholar, 12.Rosenberg K.V. et al.Decline of the North American avifauna.Science. 2019; 366: 120-124Crossref PubMed Scopus (1060) Google Scholar, 13.Senzaki M. et al.Sensory pollutants alter bird phenology and fitness across a continent.Nature. 2020; 587: 605-609Crossref PubMed Scopus (94) Google Scholar, 14.Newman J.R. Effects of industrial air pollution on wildlife.Biol. Conserv. 1979; 15: 181-190Crossref Scopus (41) Google Scholar, 15.Derryberry E.P. et al.Singing in a silent spring: birds respond to a half-century soundscape reversion during the COVID-19 shutdown.Science. 2020; 370: 575-579Crossref PubMed Google Scholar, 16.Barré K. et al.Artificial light may change flight patterns of bats near bridges along urban waterways.Anim. Conserv. 2020; (Published online August 27, 2020. https://doi.org/10.1111/acv.12635)Crossref Scopus (17) Google Scholar]. These and other impacts affect aerial species directly via physical harm (e.g., wildlife strikes or damage to their respiratory systems, due, for instance, to high levels of tropospheric ozone) or indirectly by decreasing fitness (e.g., reducing habitat quality, affecting animal communication, altering wildlife circadian rhythms and phenology) [11.Liang Y. et al.Conservation cobenefits from air pollution regulation: Evidence from birds.Proc. Natl. Acad. Sci. U. S. A. 2020; 117: 30900-30906Crossref PubMed Scopus (24) Google Scholar,13.Senzaki M. et al.Sensory pollutants alter bird phenology and fitness across a continent.Nature. 2020; 587: 605-609Crossref PubMed Scopus (94) Google Scholar]. Without global structural changes these positive short-term reductions in airspace fragmentation, climate change, and air pollutant emissions, and their positive effects on aerial wildlife, will be merely temporary [6.Gillingham K.T. et al.The short-run and long-run effects of Covid-19 on energy and the environment.Joule. 2020; 4: 1337-1341Abstract Full Text Full Text PDF PubMed Scopus (160) Google Scholar], particularly considering the need for economic recovery (Figure 1). Until now, world economic strategies have been developed at the expense of biodiversity. Historically, economic recovery in the wake of crises has caused an immediate rebound in aerial trafficvi, greenhouse gas emissions, and air pollutant emissionsiv. For instance, the last decade had the highest year-on-year increase in CO2 records since the recovery that followed the Great Recession in 2010. In the USA alone, economic recovery after the pandemic is likely to release an additional 2500 million metric tons (MMT) of CO2 from 2020 to 2035 [6.Gillingham K.T. et al.The short-run and long-run effects of Covid-19 on energy and the environment.Joule. 2020; 4: 1337-1341Abstract Full Text Full Text PDF PubMed Scopus (160) Google Scholar]. However, economic recovery should not occur at the expense of ecosystems. In particular, delays or reversals in aerial habitat protection and renewable aerial wildlife-friendly technological investments should be prevented (e.g., electric vehicles, well-designed solar power, etc.) (Table 1).Table 1Human Impact on the Aerial Habitat and the Mid- to Long-Term Potential Effects of the Post-COVID-19 Economic Recovery Measures If Designed under 'Business as Usual' or 'Build Back Better' ScenariosDriverCauses of impact'Business as usual''Build back better'viiiFragmentationMobile and stationary structures (flights, UAV, Advanced Air Mobility Project, skyscrapers, communication towers, transmission lines, wind farms).The lack of investment and disinterest in aerial wildlife- friendly infrastructure continues (including new construction of unfriendly buildings and wind farms). Unregulated aerial traffic also increases. Negative consequences impact aerial species, producing wildlife defaunation and loss of nature's contributions to people.Higher investment in the development of aerial wildlife-friendly infrastructure. Reduced and regulated aerial traffic (e.g., increased local commerce with reduced transport of goods located at a distance). Aerial species' requirements are considered and human activities produce less aerial fragmentation, wildlife defaunation, and loss of nature's contributions to people. Promotion of aerial reserves.PollutionChemical, noise, and light pollution (smog from fossil fuel, gas, and coal use, wildfires, transport, manufacturing, building and mining, artificial light at night).Increasing pollution coupled with a lack of policies, enforcement, and control. Increasing negative consequences for aerial species due to aerial habitat degradation (but also for other wildlife and human health).Policies encouraging circular economy, agroecology, and green cities (energy efficiency, more people cycling, limited use of artificial light at night and light artefacts, etc.). Strict regulations, enforcement, and control of pollution.Climate changeGreenhouse gas emissions (conventional fuel vehicles and aircraft, industries, land use change, and biomass burning).Delay and lack of investment in renewable energy, while fostering aircraft travel. Increased greenhouse gas emissions and atmospheric concentration of greenhouse gases due to traditionally fueled human mobility and land use change.Increasing investment in renewable energy production and aircraft energy efficiency, using non-fossil fuel power. Well-regulated aerial traffic and increase in remote working, the train–flight ratio, and the use of non-fossil fuel power for transport. Open table in a new tab We encourage governments to consider the aerial habitat in their post-COVID-19 agenda and plans for economic recovery, including regulation of airspace use and the potential effects of global change drivers. These drivers may produce large mid- to long-term negative effects on NCP, particularly if the associated airspace ecological processes and conservation actions are not considered after the lockdown. Thus, synergies between scientific and technology agencies, governments, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, the Convention on Biological Diversity, the International Union for Conservation of Nature, and aeronautic and energy industries are urgently needed if we are to achieve global aerial biodiversity conservation goals [3.Davy C.M. et al.Aeroconservation for the fragmented skies.Conserv. Lett. 2017; 10: 773-780Crossref Scopus (46) Google Scholar,10.Lambertucci S.A. Speziale K.L. Need for global conservation assessments and frameworks to include airspace habitat.Conserv. Biol. 2020; (Published online September 25, 2020. https://doi.org/10.1111/cobi.13641)Crossref PubMed Scopus (8) Google Scholar]. Little progress had been made in the development of conservation strategies for the skies before the pandemic; thus, we call for a new focus on the conservation of aerial habitat, particularly in the environmental and economic post-COVID-19 agenda. The positive short-term anthropause effects (on aerial habitat and wildlife) could be used as examples, providing suggestions for decision-makers (e.g., in their economic recovery plans) to turn them into long-term effects (Table 1). For instance, the implementation of aerial reserves, including controls on aerial traffic, noise, and ALAN based on species habitat requirements (e.g., Dark Sky Reserves) [3.Davy C.M. et al.Aeroconservation for the fragmented skies.Conserv. Lett. 2017; 10: 773-780Crossref Scopus (46) Google Scholar,4.Van Doren B.M. et al.High-intensity urban light installation dramatically alters nocturnal bird migration.Proc. Natl. Acad. Sci. U. S. A. 2017; 114: 11175-11180Crossref PubMed Scopus (190) Google Scholar,10.Lambertucci S.A. Speziale K.L. Need for global conservation assessments and frameworks to include airspace habitat.Conserv. Biol. 2020; (Published online September 25, 2020. https://doi.org/10.1111/cobi.13641)Crossref PubMed Scopus (8) Google Scholar], and the development of energy and mobility projects that are aerial wildlife-friendly are urgently needed [1.Voigt C.C. et al.Conservation strategies for bats flying at high altitudes.Bioscience. 2018; 68: 427-435Crossref Scopus (23) Google Scholar, 2.Lambertucci S.A. et al.Human-wildlife conflicts in a crowded airspace.Science. 2015; 348: 502-504Crossref PubMed Scopus (58) Google Scholar, 3.Davy C.M. et al.Aeroconservation for the fragmented skies.Conserv. Lett. 2017; 10: 773-780Crossref Scopus (46) Google Scholar]. Aerial conservation strategies like the reduction in CO2 emission under the Post-2020 Global Biodiversity Framework, Sustainable Development Goals, and the Paris Climate Agreement should be prioritized in multilateral environmental agreements. These measures could be developed alongside the post-COVID-19 economic recovery agenda, under the 'build back better' approach recently proposed by the Organization for Economic Co-operation and Development (OECD)viii (Figure 1). Humankind needs to think of a better way of living in harmony with nature and consider the biodiversity conservation crisis and the effects of global change when planning the recovery from the COVID-19 pandemic. We must not simply return to a 'business as usual' way of life. The 'build back better' approach (sensu OECD 2020) considers the reduction in CO2 emissions under the Post-2020 Biodiversity Framework and Paris Climate Agreement; however, it needs to foster the development of mobility and energy projects that are aerial wildlife-friendly. We now have an opportunity to rethink and reboot our way of life under the 'build back better' approach (Table 1) and this should include the protection of aerial habitats for the long-term future of biodiversity conservation and human health. We thank K.L. Bildstein, K. Cockle, J.O. Coulson, A.E.A. Stephens, and two anonymous reviews for their helpful comments. We also thank the Argentine Research Council (CONICET) for support. No interests are declared. ihttps://ipbes.net/global-assessment iiwww.nasa.gov/aeroresearch/one-word-change-expands-nasas-vision-for-future-airspace/ iiiwww.wildlife.state.nm.us/starvation-unexpected-weather-to-blame-in-mass-migratory-songbird-mortality/ ivwww.iea.org/reports/global-energy-review-2020 vhttps://wildlife.faa.gov viwww.iea.org/reports/aviation viiiwww.oecd.org/coronavirus/policy-responses/building-back-better-a-sustainable-resilient-recovery-after-covid-19-52b869f5/ ixwww.flightradar24.com/ xhttps://earthobservatory.nasa.gov/images/146481/nighttime-images-capture-change-in-china xiwww.icos-cp.eu/sites/default/files/inline-images/CovidCO2_final2.gif xiihttps://unfccc.int/ xiiiwww.cbd.int/conferences/post2020 xivhttps://sdgs.un.org/goals anthropogenic intrusions into aerial habitats that create barriers, functionally dividing the basoaerial habitat into more or less separated fragments, affecting wildlife movement. This includes permanent (e.g., buildings, windfarms) and temporal fragmentation (e.g., airplanes or drones). anthropogenic contamination of aerial habitats, which degrades their natural condition (e.g., noise, light, gases), affecting wildlife movement and communication, as well as biodiversity and human health. area of conservation biology that seeks to understand the anthropogenic impacts on aerial habitats. It aims to evaluate how those impacts affect the survivorship, behavior, and diversity of aerial species and to develop conservation tools for aerial habitats and biodiversity. the dramatic reduction in human activity and goods production caused by the COVID-19 pandemic. all the contributions of living nature, both positive and negative, to people's quality of life. Positive contributions include, food provision, water purification, and artistic inspiration among others, whereas negative contributions include disease transmission or predation that can harm people or their assets. chemical compounds, such as carbon monoxide (CO), methane (CH4), non-methane volatile organic compound (NMVOC), and nitrogen oxide (NOx), which in the presence of solar radiation react with other chemical compounds to form ozone, mainly in the troposphere. the global framework to avoid dangerous climate change by limiting global warming to well below 2°C above preindustrial levels and to pursue efforts to limit the temperature increase even further to 1.5°Cxii. the framework of the Convention on Biological Diversity, which will be adopted during the 15th meeting of the Conference of the Partiesxiii. the plan guiding the actions needed to achieve a better and sustainable future over the next 15 years in 17 areas of critical importance for humanity and the planetxiv.