IMPACTS ON BIODIVERSITY AND ECOSYSTEMS FROM CONVENTIONAL EXPANSION OF FOOD PRODUCTION

The Earth’s natural environment provides the platform upon which all life is based. Ecosystems provide regulating as well as supporting services that are essential for agriculture and fisheries. These include provisioning of food, fibre and water; regulating services such as air, water and climate regulation, pollination and pest control; and providing resilience against natural disasters and hazards. Despite its crucial role in providing food, agriculture remains the largest driver of genetic erosion, species loss and conversion of natural habitats. Globally, over 4,000 assessed plant and animal species are threatened by agricultural intensification, and the number is still rising. Over 1,000 (87%) of a total of 1,226 threatened bird species are impacted by agriculture. Overfishing and destructive fishing methods along with eutrophication caused by high nutrient run-off from agricultural areas are among the major threats to inland and marine fisheries.

If increase in food production is to be met only by indiscriminate expansion of cropland area, intensification of yields using artificial fertilizers and pesticides and by increasing harvest beyond sustainable levels, we may further erode the platform upon which food production is based. Finding alternatives to the use of cereal in animal feed, recycling of waste for feed and energy recovery, and reducing the use of croplands for non-food purposes will not only increase food energy efficiency in production, but will also greatly help to preserve biodiversity and other natural resources, and the human communities and cultures that they support.

ECOSYSTEM SERVICES

Ecosystems have been described as the life support system of the Earth – for humans as well as all life on this planet (MA Health Synthesis Report 2005). Ecosystem services, the benefits that humans derive from ecosystems, are considered “free”, often invisible, and are therefore not usually factored into decision-making. This chapter discusses the role of the diverse forms of living species – biodiversity – in food production, focusing on agriculture and marine capture fisheries, as these provide the bulk of global food production. 

Agriculture (livestock and foodcrops) require a range of conditions for optimum productivity. These conditions are generated by natural ecological components and processes as well as through artificial enhancement. 

Water resources for agriculture are highly dependent on natural ecosystems and biodiversity, in particular vegetation such as forests in terms of flow regulation. This is crucial for providing a dependable water supply to crop areas, such as through retention of water in wetlands and forests buffering both droughts and floods (Bruijnzeel, 2004; UNEP, 2005). At present 75% of globally usable freshwater supplies comes from forested catchments (Fischlin et al., 2007), therefore water is critically linked to forests. These ecosystems also help buffer global climate change (Nepstad et al., 2007).

Genetic diversity plays a critical role in increasing and sustaining food production levels and nutritional diversity. Diverse organisms contributing to soil biodiversity perform a number of vital functions that regulate the soil ecosystem, including decomposition of litter and cycling of nutrients such as nitrogen. Crop rotations or agroforestry increase yield stability and soil fertility; grassland and pasture/crop systems tend to be more sustainable because they provide opportunities for rotation diversity. Biodiversity may create “pest suppressive” conditions and greater resistance to invasion of farming systems by noxious species. Pollinators are essential for the production of a large number of crops (e.g., cereal, orchard, horticultural and forage production), and contribute to improvements in quality of both fruit and fiber crops; this service is ensured by an abundance and diversity of pollinators, in large part provided by wild biodiversity.

Figure 25: A photographic impression of the gradual changes in two ecosystem types (landscape level) from highly natural ecosystems (90–100% mean abundance of the original species) to highly cultivated or deteriorated ecosystems (around 10% mean abundance of the original species). Locally, this indicator can be perceived as a measure of naturalness, or conversely, of human-impact. (Source: CBD, 2008; Alkemade et al., 2009).

Pest control is another key ecosystem service underpinned by biodiversity; it is greatly determined by the abundance of natural enemies of the pest species involved.Improved pest control is dependent on a diversity of natural enemies of pests, and non-crop habitats are fundamental for the presence and survival of these biological control agents (predators, parasitoids) (Zhang et al., 2007). Landscape diversity or complexity, and proximity to semi-natural habitats tend to produce a greater abundance and species richness of natural enemies (Bianchi et al., 2006; Kremen and Chaplin-Kramer 2007; Tscharntke et al., 2007; Balmford et al., 2008). Thus, the main threat to the provision of biological control as an ecosystem service seems to be habitat loss and degradation, now exacerbated by potentially disruptive climate change. Indeed, Balmford et al., (2008) suggest that there is a medium to high probability that the provisioning of biological control is subject to thresholds/tipping points in the foreseeable future (by 2025), particularly in regions of very intensively managed agriculture.

ENVIRONMENTAL COSTS OF CONVENTIONAL INTENSIFICATION AND EXPANSION OF FOOD PRODUCTION

EXPANSION OF CROP- AND RANGELANDS

Modern agricultural methods and technologies brought spectacular increases in food production (Tilman et al., 2002), but not without high environmental costs. Efforts to boost food production, for example, through direct expansion of cropland and pastures, will negatively affect the capacity of ecosystems to support food production and to provide other essential services. Food production will undoubtedly be affected by external factors such as climate change, but the production and distribution of food is itself is also a major cause of climate change.

Despite its crucial role in feeding the world population, agriculture remains the largest driver of genetic erosion, species loss and conversion of natural habitats (MA, 2005). The conversion of natural habitats to cropland and other uses typically entails the replacement of systems rich in biodiversity with monocultures or systems poor in biodiversity. Large-scale agriculture brings ecosystem simplification and loss of (bio)diversity, thus reducing the potential to provide ecosystem services other than food production. Of some 270,000 known species of higher plants, about 10,000 –15,000 are edible and only about 7,000 are used in agriculture. However, globalization and agricultural intensification have diminished the varieties traditionally used, with only 30% of the available crop varieties dominating global agriculture. These, together with only 14 animals species, provide an estimated 90% of the world’s consumed calories (FAO,1998).

Habitat modification through agriculture and a variety of other causes is, in general, the most important factor in increasing species’ risk of extinction. Most of this habitat loss arises from encroaching farmland and habitat conversion for food and biofuel production (Figures 25, 26 and 27). Clearance for cropland or permanent pasture has reduced the extent of natural habitats on arable land by more than 50% (Green et al., 2005), with much of the rest altered by temporary grazing (Groombridge and Jenkins, 2002). Habitat modification already affects more than 80% of the globally threatened mammals, birds and plants (Groombridge and Jenkins, 2002), with serious implications for ecosystem services and human wellbeing. Indeed, the most significant threat by far to the world’s 5,500 mammal species is habitat loss, with over 2,000 (40%) species being negatively impacted (IUCN, 2008). Globally, over 4,000 of the assessed plant and animal species are threatened by agricultural intensification (IUCN, 2008). With continuing agricultural expansion, this number has increased to over 4,600 species, and is still rising. The IUCN Global Red List (IUCN, 2008) includes 457 of the globally assessed plants and animals that are threatened by agriculture in Sub-Saharan Africa. Of these, 65 are critically endangered and 182 endangered. Similarly, 683 species are threatened by agriculture in Latin America, of which 146 are critically endangered and 244 endangered.

Globally, over 1,000 (87%) of a total of 1,226 threatened bird species are impacted by agriculture. More than 70 species are affected by agricultural pollution, 27 of them seriously. Europe’s farmland birds have declined by 48% in the past 26 years (European Bird Census Council, 2008). Pesticides and herbicides pose a threat to 37 threatened bird species globally (BirdLife, 2008), in addition to deleterious effects of agricultural chemicals on ground water (Bexfield, 2008).

Domesticated species diversity is also under threat. Worldwide, 6,500 breeds of domesticated mammals and birds are under immediate threat of extinction, reducing the genetic diversity for options in a changing environment (Diaz et al., 2007; MA, 2005). 

With the loss of biodiversity in both natural and agricultural systems comes the loss of other ecosystem services. In addition to food, fibre and water provisioning, regulating services such as air, water and climate regulation, water purification, pollination and pest control, as well as providing resilience against natural hazards and disasters and environmental change, are among the numerous examples of ecosystem services being lost under increasing intensification and expansion of agriculture.

Loss of global biodiversity with unsustainable conventional expansion of cropland

A central component in preventing loss of biodiversity and ecosystem services, such as provisioning of water, from expanding agricultural production is to limit the trade-off between economic growth and biodiversity by stimulating agricultural productivity and more efficient land use. Further enhancement of agricultural productivity (‘closing the yield gap’) is the key factor in reducing the need for land and, consequently, the rate of biodiversity loss (CBD, 2008). This option should be implemented carefully in order to not cause additional undesired effects, such as emissions of excess nutrients and pesticides and land degradation. An increase in protected areas and change towards more eco-agricultural cropping systems and sustainable meat production could have immediate positive effects on both biodiversity and water resource management, while increasing revenues from tourism (CBD, 2008).

 
Figure 26: Projected land use changes, 1700–2050. (Source: IMAGE). Figure 27: Loss of biodiversity with continued agricultural expansion, pollution, climate change and infrastructure development. (Source: GLOBIO; Alkemade et al., 2009).

IMPACTS FROM INTENSIFICATION OF CROPLANDS

Intensive management to increase agricultural production – through irrigation and the application of fertilizers and pesticides – can further reduce the wildlife value of farmed land. From 1961 to 1999, the area of land under irrigation nearly doubled; the use of nitrogenous and phosphate fertilizers increased by 638% and 203%, respectively, and the production of pesticides increased by 854% (Green et al., 2005). Such intensification has had major direct impacts on biodiversity, such as on farmland birds (Figure 28) and aquatic species. Large-scale use of fertilizers and pesticides, coupled with fragmentation and losses of important farmland habitat qualities, also reduces the number of flowers and plant diversity, diminishes insect biodiversity, and subsequently the survival of farmland birds, particularly the young that are dependent upon insects in their first weeks or months of life (see box).

Loss of European Birds with agricultural intensification

Europe’s common farmland birds declined severely during the past 26 years. Their average breeding populations in 2006 were about 50% lower than in 1980, and there is no sign of recovery. Farmland birds have suffered most in western Europe, which has the longest history of agricultural intensification. The countries of central and eastern Europe, which joined the European Union (EU) more recently (in 2004 or 2007), have not yet sustained such large losses of farmland birds, but their numbers are declining and are already much lower than in the 1980s. Agricultural intensification, such as the loss of crop diversity, destruction of grasslands and hedgerows, and excessive use of pesticides and fertilizers, has been widely recognised as one of the main driving forces behind this dramatic decline of common farmland birds. A transformation of the EU Common Agricultural Policy into a sustainable land management and rural development policy, thereby stopping the distribution of environmentally harmful subsidies, may prevent further declines of farmland bird populations.

Figure 28: Farmland birds in Europe have declined dramatically in the last decades, mainly as a result of agricultural intensification. (Source: RSPB, European Bird Census Council (EBCC) and the Pan-European Common Bird Monitoring Scheme (PECBMS).

Aquatic ecosystems are also being widely affected by food production in terrestrial areas, through high nutrient inputs (Seitzinger and Lee, 2008) in run-off from agricultural and livestock production and alteration of freshwater flows. The ensuing reduction in water quality (Mitchell et al., 2005) is evident in increased eutrophication and subsequent algal blooms and oxygen-deficient waters, which when extreme, could result in dead zones (UNEP, 2001; 2008). In the northwestern Gulf of Mexico, nutrient enrichment mainly from fertilizer use in the Mississippi Basin has accounted for the world’s largest hypoxic or dead zone (Turner and Rabalais 1991; Rabalais et al., 1999; UNEP, 2008). Without significant nitrogen mitigation efforts, marine areas will be subjected to increasing hypoxia and harmful algal blooms that will further degrade marine biomass and biological diversity (Sherman and Hempel, 2008; UNEP, 2008). 

In some regions, diversion of water for agricultural and other purposes has reduced river flow to coastal areas, with severe impacts on coastal habitats and estuarine-dependent species. For example, damming of the Colorado River has drastically changed what used to be an estuarine system into one of high salinity and reduced critical nursery grounds for many commercially important species, including shrimp (Aragón-Noriega and Calderon-Aguilera, 2000). There are many well-documented examples where diversion of water for agriculture has degraded and reduced the extent of inland water bodies (e.g., the Aral Sea), affecting fish spawning and migration and causing a collapse of the fishing industry and a loss of species diversity in the affected areas (MA, 2005).

With current scenarios from the CBD, all regions of the world will continue to experience loss in biodiversity, with Africa, followed by Latin America and the Caribbean, experiencing the highest losses as a result of major land use changes (especially in increases in pastures and biofuel production) combined with increasing land degradation. Large areas of Africa are projected to lose more than 25% of mean species abundance by 2050 (UNEP, 2007). According to FAO’s Global Perspective Unit (2008), at present 228 million ha of arable land are in use in Sub-Saharan Africa. Potentially, this area can be increased to over 1 billion ha of suitable land for rainfed crops in Africa by 2030. Likewise, in South America similar scenarios project the present 208 million ha in agricultural use to be increased to over 1 billion ha by 2030 at the expense of natural ecosystems. These expansions will have huge costs to biodiversity.

 

Enhancing sustainability through the use of crop wild relatives

Crop wild relatives (CWR) – species or other taxa more or less closely related to crops, which include most of the progenitors of our domesticated types – have made a very significant contribution to modern agricultural production through the characteristics that they have contributed to plant cultivars.

Over the last 100 years, crop wild relatives have become increasingly important as sources of useful genes. For example, they have contributed resistance to pest and disease (e.g,. resistance to late blight in potato and grassy stunt virus in rice, which came from a single accession of Oryza nivara found in Orissa, India) and to abiotic stress. They have also increased nutritional values such as protein and vitamin content. The economic returns from investment in CWR can be striking; for example, genetic material from a tomato wild relative has allowed plant breeders to boost the level of solids in commercial varieties by 2.4%, which is worth US$250 million annually to processors in California alone (FAO, 1998).

The natural populations of many crop wild relatives are increasingly at risk, mainly from habitat loss, degradation and fragmentation. Moreover, the increasing industrialization of agriculture is reducing populations of crop wild relatives in and around farms. They are often missed by conservation programmes, falling between the efforts of agricultural and environmental conservation actions. A major global effort, coordinated by Bioversity International and supported by UNEP GEF, to find ways of securing the improved conservation of crop wild relatives is in progress in 5 countries (Armenia, Bolivia, Madagascar, Sri Lanka and Uzbekistan) in collaboration with a number of international agencies (FAO, UNEP-WCMC, IUCN and Botanic Gardens Conservation International – BGCI)

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