Title Considering LandSea Interactions and Trade offs for Food and Biodiversity Running head LandSea Interactions for Food Security List of Authors
Year: 2017

With the human population expected to near 10 billion by 2050, and diets shifting towards greater per capita consumption of animal protein, meeting future food demands will place ever growing burdens on natural resources and those dependent on them. Solutions proposed to increase the sustainability of agriculture, aquaculture, and capture fisheries have typically approached development from single sector perspectives. Recent work highlights the importance of recognising links among food sectors, and the challenge cross sector dependencies create for sustainable food production. Yet without understanding the full suite of interactions between food systems on land and sea, development in one sector may result in unanticipated trade offs in another. We review the interactions between terrestrial and aquatic food systems. We show that most of the studied land sea interactions fall into at least one of four categories: ecosystem connectivity, feed interdependencies, livelihood interactions, and climate feedback. Critically, these interactions modify nutrient flows, and the partitioning of natural resource use between land and sea, amid a backdrop of climate variability and change that reaches across all sectors. Addressing counter productive tradeoffs resulting from land sea links will require simultaneous improvements in food production and consumption efficiency, while creating more sustainable feed products for fish and livestock. Food security research and policy also needs to better integrate aquatic and A cc ep te d A rt ic le This article is protected by copyright. All rights reserved. terrestrial production to anticipate how cross sector interactions could transmit change across ecosystem and governance boundaries into the future.  Population growth and dietary shifts towards greater consumption of animal protein are expected to increase current human food demand by over 50% in the next 30 years (Alexandratos Bruinsma, 2012; Tilman Clark, 2014) Meeting these demands through further intensification and expansion of terrestrial, freshwater, and marine food production threatens global biodiversity and the structure and function of natural ecosystems (Brussaard et al. 2010) Creeping loss of environmental services from natural habitat destruction undermines the integrity of the human and natural components of our food system (Ostrom, 2009) and poses a huge threat to the food security of millions of people. Thus, there is an urgent need to understand the social ecological trade offs from a variety of development pathways proposed to meet future food demands. Meeting future consumption demands will require development across all food production sectors. On land, genetic modification, increased waste efficiency, or integrated pest management strategies can close the gap between realized and maximum potential crop yields (Godfray et al. 2010; Godfray Garnett, 2014; Tilman, Balzer, Hill, Befort, 2011) Better fisheries management throughout the global ocean, and advances in aquaculture feed technologies may also allow per capita fish consumption to increase, while reducing impacts on aquatic resources (Bene et al. 2015; FAO, 2016; Jennings et al. 2016) Yet, the challenge is not isolated to increasing production alone. Improving food security for 800 million people living in hunger worldwide requires tackling barriers to food access (Sen, 1981) Overcoming disparities in access requires vast improvements in gender equity, trade reforms, and natural A cc ep te d A rt ic le This article is protected by copyright. All rights reserved. resource management as highlighted by the United Nations Sustainable Development Goals (FAO IFAD WFP, 2015; United Nations, 2015b) Most solutions, however, continue to focus on a combination of single sector approaches to development including both aquatic and terrestrial food systems but largely ignore the human dependencies that reach across multiple sectors and ecosystems. Interactions among species or functional groups within ecological food webs are widely recognised as fundamental in determining system wide responses to perturbations (Marzloff et al. 2016; Suttle, Thomsen, Power, 2007) Here we apply the same thinking to an integrated global food system, with interacting marine, freshwater, and terrestrial sectors (fisheries, aquaculture, and agriculture) burdened by population growth, shifting diets, and climate change. Interactions among food sectors have pivotal roles in the transfer of impacts from one region to another via the disruption of environmental services and trade, or from human adaptation strategies that shift resource use (Warren, 2011) Interactions between fisheries and aquaculture in the marine environment have been the focus of a substantial body of research in recent years (e.g. Naylor et al. 2000; Arechavala Lopez et al. 2013; Natale et al. 2013) Nevertheless, the links and interactions spanning food systems and ecosystems on land and sea remain vastly understudied. Lack of integration is not surprising given organizational and institutional norms, structures, and incentives that lend to specialised knowledge within disciplines (Viseu, 2015) thus silo approaches to management. Nonetheless, we need a new perspective on sustainable development of the food system that incorporates how development in one sector can affect another. Recent work highlights how links and interdependencies connecting food sectors on land and sea present challenges for sustainable food production (Blanchard et al. 2017) Yet, the full scope of land sea interactions among food production systems is not understood. To A cc ep te d A rt ic le This article is protected by copyright. All rights reserved. address this gap, we review the suite of interactions connecting terrestrial and aquatic (both marine and freshwater) production systems to highlight connectivity, and discuss the socialecological trade offs that result from various intensification strategies (see 'S1 Supplementary Information' for review methods) We show that four main pathways link food sectors on land and sea: ecosystem connectivity, feed interdependencies, livelihood interactions, and climate feedback  Ecosystem Connectivity Terrestrial, freshwater, and marine habitats are inextricably linked through the energy, material, or organisms that pass between them (Gorman, Russell, Connell, 2009) Rivers and streams play a fundamental role in the flow of subsidies across the land sea interface (Tallis, Ferdana, Gray, 2008) and are pivotal in transferring impacts between systems. The asymmetric flow of water from land to sea means changes in habitat structure on land may be of greater consequence for aquatic systems than vice versa (Alvarez Romero et al. 2011) Water extraction for agriculture can pose significant threats to ecosystems and human activity downstream (Atapattu Kodituwakku, 2009) Agriculture accounted for 92% of global freshwater consumption from 1992 2005, primarily through irrigation (Hoekstra Mekonnen, 2012) Upstream water extraction and irrigation schemes reduce water flow otherwise delivered to coastal ecosystems with considerable impact on downstream fisheries. Reductions in lateral flooding and increases in salt water intrusion limit the capacity for wetlands to support both biodiversity and productive fisheries, and has been a major source of conflict in deltaic areas in Asia, Africa, and Australia (Craig, Halls, Barr, Bean, 2004; Islam Gnauck, 2008; Lemly, Kingsford, Thompson, 2000) A cc ep te d A rt ic le This article is protected by copyright. All rights reserved. Terrestrial farming also influences the structure and function of aquatic systems worldwide through major changes to land use. Conversions of forests, grasslands or wetlands to grazing or arable land are the most common (Galloway et al. 2010) Changes in vegetative cover influence hydrological processes such as infiltration, which if decreased, increases surfacerun off and disrupts vegetative nutrient uptake (Galloway et al. 2010) Hydrological alteration and changes to nutrient loading by crop livestock systems are the single largest source of disruption to nitrogen and phosphorous flows between ecosystems (Bouwman et al. 2013) Global, regional and local transfers of nitrogen have undergone dramatic transition since the Haber Bosch process allowed humans to convert non reactive nitrogen gas to ammonia for use in synthetic fertilisers (Galloway et al. 2003, 2010) Globally, crop systems receive 75% of all reactive nitrogen compounds created by humans. The vast majority of fertilisers applied are lost to waterways and the atmosphere only 20% of nitrogen delivered to arable land reaches livestock, less than 10% directly contributes to human food. Moreover, on a global basis approximately 85% of nitrogen fed to cattle is lost in manure and waste (Galloway et al. 2003, 2010; Smil, 2002) Manure stored in earthen ponds then leach massive quantities of nutrients into groundwater and waterways, exacerbating nitrogen deposition in aquatic environments (Kato, Kuroda, Nakasone, 2009; Tilman, Cassman, Matson, Naylor, Polasky, 2002) Diffusing into rivers and streams, agricultural run off is a major driver of biodiversity loss in aquatic habitats worldwide. Inputs of sediment and nutrients act synergistically, leading to reductions in water quality, and alterations to deposition and flow in adjacent freshwater environments (Dudgeon et al. 2006) In Europe and North America, smothering of fish nests or 'redds' can also affect the recruitment of commercially important anadromous fish such as salmon (Heaney, Foy, Kennedy, Crozier, O' Connor, 2001) A cc ep te d A rt ic le This article is protected by copyright. All rights reserved. Anthropogenically mobilized nitrogen and phosphorous in aquatic environments make their way downstream to coastal waters and are a substantial source