20. Agricultural Systems: Biodiversity in Domesticated Landscapes

As the global population expands, seemingly inexorably, toward 9 billion, it is widely accepted that global food production will need to increase by at least 50% to feed the growing population and improve the living standards for billions of people. Even more challenging, this must be done in the face of climate change, which makes agricultural productivity highly unpredictable. Food demand may grow even faster than human population, as a result of growing urbanization, rising incomes, and greater efforts to reduce hunger among the estimated 950 million people currently under-nourished (FAO, 2008c). Global consumption of livestock products is predicted to exceed 650 million tonnes by 2020. More land will surely be required to grow crops and graze livestock, even more so as biofuels are expected to become a greater contributor to meeting energy needs. In Africa alone, land devoted to cereal production is expected to increase from over 100 million hectares in 1997 to about 135.3 million hectares in 2025, inevitably involving trade-offs among land devoted to crops, livestock, and other purposes.

Feeding a human population of 9 billion using current methods could require converting another one billion hectares of natural habitat to agricultural production, primarily in the developing world, together with a doubling or tripling of nitrogen and phosphorous inputs, a two-fold increase in water consumption and a three-fold increase in pesticide use. A serious limiting factor is expected to be water, as 70% of the freshwater used by people is already devoted to agriculture. Scenarios prepared by the Millennium Ecosystem Assessment (MA) thus suggest that agricultural production in the future will need to focus more explicitly on ecologically-sensitive management systems that give greater attention to biodiversity (Carpenter et al., 2005).

Whether increased agricultural production is accomplished through more intensive use of existing agricultural land or more extensive use of lands that are currently being used for other purposes, biodiversity inevitably will come under increased pressure.

Agriculture can be defined as the art, science and business of raising livestock and cultivating soil to produce crops. It is totally dependent on genes, species and ecosystems and the variability they contain. This biodiversity also provides agriculture with the capacity to adapt to changing conditions.

The conservation movement is now considering how it wishes to relate to agriculture in the most productive manner. After all, farmers, pastoralists, and hunter-gatherers are the occupiers of the rural landscapes where most of the world's biodiversity survives. If we hope to maintain global biodiversity and a reasonable balance between people and the rest of nature, then agriculture needs to be part of the conversation.

On the other hand, conservation has much to contribute to sustainable agriculture. Such agriculture should be highly diverse, requiring supporting ecosystems that comprise a wealth of wild species of benefit to agriculture. These include wild relatives of domesticated plants, pollinators, species useful for pest control, soil micro-organisms, and many others.

Nearly one-third of our planet's land is dominated by agricultural crops or planted pastures, thus having a profound ecological effect on the whole landscape. Another 10–20% of land is under extensive livestock grazing, and around 1–5% of food is produced in natural forests (Cassman and Wood, 2005). The biodiversity and ecosystem services involving agriculture are therefore critical to ensuring a sustainable future for our farmers.

HOW BIODIVERSITY SUPPORTS THE GROWING DEMAND FOR AGRICULTURAL PRODUCTION

Virtually all domesticated species of plants and animals still have wild relatives whose genetic diversity can be valuable in enabling the domesticated species to adapt to changing conditions. While national and international seed banks contain much valuable genetic material, the wild relatives are especially important because they are living and adapting to changing climate conditions, in competition with other species, predators, and new diseases. Efforts to conserve wild relatives of domesticated plants and animals have greatly increased over the past few decades, international agreements now recognize their value, numerous projects have been launched in various countries, and institutional collaboration is expanding (Meilleur and Hodgkin, 2004). Within IUCN, the Species Survival Commission (SSC) now has a Specialist Group working on wild relatives of domesticated plants, and several of its other Specialist Groups deal with wild relatives of domesticated animals (e.g. Wild Cattle, Camelids, Pigs and Peccaries, Pheasants).

An especially important supporting service provided to agriculture by biodiversity is plant protection. Plants respond to insects feeding on their leaves by synthesizing and releasing complex blends of volatile compounds, which attract insects that are natural enemies of the insects who are feeding on the leaves, thereby helping defend the plant. If the biodiversity-based natural defences of plants could be more effectively mobilized, safe and effective crop protection strategies could be designed that would significantly minimize the negative side-effects of the current generation of chemical fertilizers.

Many of the world's most important watersheds are densely populated and under predominantly agricultural use, and most of the rest are in agricultural land-use mosaics where crop, livestock and forest production influence hydrological systems. In such regions, agriculture can be managed to maintain critical watershed functions, such as maintaining water quality, regulating water flow, recharging underground aquifers, mitigating flood risks, moderating sediment flows, and sustaining freshwater species and ecosystems. Effective water management encompasses the choice of water-conserving crop mixtures, soil and water management (including irrigation), vegetation barriers to slow movement of water down slopes, year-round soil vegetative cover, and maintenance of natural vegetation in riparian areas, wetlands and other strategic areas of the watershed. Well-managed biodiversity-rich agricultural landscapes can also provide protection against extreme natural events. With water scarcity and extreme weather events predicted to increase in the coming decades in many parts of the world, the contribution of biodiversity to enhancing the capacity of agricultural systems to sustain watershed functions is likely to be one of the most important considerations in agricultural investment and management.

Agricultural landscapes can conserve a broad range of native terrestrial species, especially those that adapt well to habitat fragmentation and agricultural land use. The prospects for conserving biodiversity in agricultural landscapes depends on the degree of fragmentation and functional connectivity of natural areas, the habitat quality of those areas, the habitat quality of the productive matrix, and the extent to which farmers manage their land to conserve biodiversity. Forms of agriculture that successfully balance productivity, improved livelihoods, and biodiversity conservation at a landscape scale have been termed “ecoagriculture” (McNeely and Scherr, 2003).

Efforts to maintain natural habitats in farming areas are longstanding, principally through agricultural set-aside schemes, crop rotation, leaving some land fallow, and including trees in the farmstead. Land withdrawn from conventional production of crops has been shown unequivocally to enhance biodiversity in North America and Europe (van Buskirk and Willi, 2004). For many commercial crop monocultures, leaving field margins uncultivated for habitat protection does not reduce total yields, as inputs are applied more economically on the rest (Clay, 2004).

However, landscape-scale interventions specifically designed to protect habitats for biodiversity are much more effective than a farm-by-farm approach. A recent review of evidence from North America on how much wildlife habitat is “enough” in agricultural landscapes (Blann, 2006) concluded that habitat needs must be considered within the landscape history and context. Habitat patches must be large enough and connected to other patches, for example along rivers and streams or steep, hilly lands that are covered in native vegetation. Smaller patches of natural habitat may be sufficient if adjacent agricultural patches are ecologically managed. A growing body of research shows that landscape connectivity between large patches of forest can be effectively maintained through retention of tree cover on the farm, such as live fences, windbreaks, and hedges in grazing lands and agricultural fields (Harvey et al., 2004). Biodiversity conservation efforts designed to adapt to changes in agricultural landscapes should therefore focus on protecting (or restoring) large areas of native habitat within the agricultural matrix, and retaining elements (such as hedgerows, isolated trees, riparian forests and other non-cropped areas) that enhance landscape connectivity. Such measures will ensure heterogeneity at both field and landscape levels, thereby enhancing the adaptability of agricultural ecosystems in the face of climate change, new demands for new crops, demographics, and other dynamic factors.

THE FUTURE OF BIODIVERSITY AND AGRICULTURE

From a wild biodiversity conservation perspective, the ideal agricultural production systems mimic the structure and function of natural ecosystems (Blann, 2006; Jackson and Jackson, 2002). In humid and sub-humid forest ecosystems, farms would resemble forests, with productive tree crops, shade-loving understorey crops, and agroforestry mixtures; in grassland ecosystems, production systems would rely more on perennial grains and grasses, along with economically useful shrubs and dryland tree species. Annual crops could be cultivated in such systems, but as intercrops, or monoculture plots interspersed in mosaics of perennial production and natural habitat areas. Domesticated crop and livestock species' diversity would be encouraged at a landscape scale, and genetic diversity within species would be conserved in situ at a large ecosystem scale, to ensure system resilience and the ecological diversity required to adapt to changing conditions.

Box 20.1 Cabrucas: conserving bats while producing cacao

In Bahia State, Brazil, traditional shade plantations of cacao (known locally as “cabrucas”) also provide habitat for many forest-dwelling species, including a rich and abundant bat community that feeds on many species of insects and helps pollinate night-blooming species of plants. But when the cabrucas are located more than one kilometre from native forests, the bat communities are less diverse than those found in forests. Therefore, the entire landscape should be considered for management, taking into account that maintenance of cabrucas together with the preservation and restoration of forest patches is essential to the conservation of bat diversity.

Source: Schroth and Harvey, 2007

Multi-storey agroforestry systems, tree fallows and complex home gardens are especially rich in wild biodiversity. For example, canopy height, tree, epiphyte, liana and bird species diversity, vegetation structural complexity, percentage ground cover by leaf litter, and soil calcium, nitrate nitrogen and organic matter levels in topsoils are all significantly greater in shaded than in sun-grown farms, while air and soil temperatures, weed diversity and percentage ground cover by weeds are significantly greater in farms without trees. In Central America, complex polyculture combinations and management systems enhance the productivity of coffee, cocoa, banana, timber and other commercial tree products.

While coffee grown in monoculture plantations with full exposure to the sun has higher yields, coffee grown in the shade is far more beneficial for sustainable agriculture and conserving biodiversity (often supporting more than twice as many species of birds). Systems with many species of trees providing shade also help support beneficial insects, orchids, mammals, and other species, as well as protecting fragile tropical soils from erosion, providing nutrients, and suppressing weeds, thereby reducing or eliminating the need for chemical herbicides and fertilizers and thus reducing farming costs. Farmers also are able to harvest various species of fruits, firewood, lumber, and medicines from the shade trees.

To replace crops that must be replanted each year (usually as monocultures, where a single species is planted over an extensive area), new and improved perennial crops, such as fruits, leafy vegetables, spices, and vegetable oils, are becoming more popular. Perennial crops can be more resilient and involve less soil and ecosystem disturbance than annual crops, and provide much greater habitat value, especially if grown in mixtures and mosaics (Jackson and Jackson, 2002).

Strategic planning for agricultural development has begun to focus on adaptation of systems to climate change, anticipating rising temperatures and more extreme weather events. With each one degree Celsius increase in temperature during the growing season, the yields of rice, wheat and maize drop by about 10% (Brown, 2004). Cash crops such as coffee and tea, requiring cooler environments, will also be affected, forcing farmers of these crops to move higher up the hills, clearing new lands as they climb. Montane forests important for biodiversity are likely to come under increasing threat as a result. Effective responses to climate change will require changing varieties, modifying management of soils and water, and developing new strategies for pest management as species of wild pests, their natural predators, and their life-cycles alter in response to changing climates. Increasing landscape and farm-scale diversity are likely to be an important response for reducing risks and adapting to change.

“An especially important supporting service provided to agriculture by biodiversity is plant protection.”

Since the 1960s both industrial agriculture in developed countries and the original Green Revolution in developing countries have depended on improved seeds, chemical fertilizers and pesticides, and irrigation. This production model involved a small number of crops, generally in monoculture stands (to increase efficiency in use of external inputs and mechanization). Wild flora and fauna were considered direct competitors for resources or harvested products, while water was diverted from wetlands and natural habitats for irrigation. But over the past two decades, research has demonstrated the value of agricultural biodiversity in all its forms, including crop and livestock genetic diversity, associated species important for production (for example, pollinators, soil micro-organisms, beneficial insects, and predators on pests) and wild species who find their home in agricultural landscapes (Uphoff et al., 2006).

A variety of modern approaches that encourage biodiversity have arisen from various disciplines, philosophies, or geographical conditions. Biodiversity-friendly alternatives to industrial agriculture include agroecology (Altieri, 1995), conservation agriculture (FAO, 2001a), organic agriculture (IFOAM, 2000) and sustainable agriculture (Pretty, 2005). They have tended to focus on maintaining the resource base for production, through managing nutrient cycles, protecting pollinators and beneficial micro-organisms, maintaining healthy soils and conserving water. They seek to reduce the ecological “footprint” of farmed areas and the damage to wild biodiversity from toxic chemicals, soil disturbance and water pollution. In many ways, they resemble pre-industrial forms of farming, but benefit from modern approaches that enhance yields and labour productivity while still maintaining biodiversity.

Organic farming aids biodiversity by using fewer pesticides and inorganic fertilizers, and by adopting wildlife-friendly management of habitats where crops are not being grown, including strategies such as not weeding close to hedges and by mixing arable and livestock farming. Mixed farming particularly benefits some bird species, including those that nest in crops. Some farms that adopt selected organic practices, such as replacing chemical weeding with mechanical methods, may encourage biodiversity as much as completely organic farms.

The future of agriculture will depend heavily on contributions from women. Women are the main producers of the world's staple crops (rice, wheat, maize) that provide up to 90% of the rural poor's food intake and produce 60–80% of food in most developing countries. In India, women provide 75% of the labour for transplanting and weeding rice, 60% for harvesting, and 33% for threshing. (Press releases from the United Nations Information Centre in Sydney for Australia, New Zealand, and the South Pacific 1995 as cited in Mata & Sasvari, 2009).

According to the Food and Agriculture Organization (FAO), women produce, select and save up to 90% of seeds and germplasm that are used as planting material in smallholder agricultures. In Rwanda, women produce more than 600 varieties of beans, and Peruvian Aguaruna women cultivate more than 60 varieties of manioc (FAO, 2001b).

According to the Yemen National Biodiversity Strategy and Action Plan (NBSAP) women also have a key role in growing and preserving underutilized species, which do not satisfy a large proportion of the world's food needs, but are used by specific communities to complement their diets. In Yemen, women grow different crops from men, identified as “women's crops”, such as groundnuts, pumpkins, leafy vegetables, cowpeas, cucumbers and sweet potatoes, which has the effect of raising farm biodiversity and food security (NBSAP Yemen, 2005). NBSAP Bhutan recognized that underused species contribute substantially to household food and livelihood security; they are often managed or harvested by women. Knowledge of the uses and management of these species is likewise localized and specialized (NBSAP Bhutan, 2002).

In the coming decade, the conservation community, working in closer cooperation with agricultural organizations, should seek sustainable and adaptable forms of land use that give high priority to conserving wild relatives of domestic plants and animals (noting that many of these are threatened species). Incorporating compatible forms of agriculture in landscape-level biodiversity conservation strategies and action plans will require building the expertise of farmers as ecosystem managers and publicizing the multiple values of biodiversity in supporting agriculture, thereby helping to build support for conservation.

Biodiversity and ecosystem services should be incorporated into agricultural research and development to ensure that new agricultural technologies support conservation of biodiversity rather than threatening it. Finally, developing new approaches to paying farmers for their contributions to conserving biodiversity and maintaining ecosystem services will help provide the necessary incentives for consolidating conservation and agriculture pursuits.

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