GLOBAL LANDUSE CHANGE AND SCENARIOS OF BIODIVERSITY LOSS
Modern agricultural methods and technologies brought spectacular increases in food production, but are also a primary cause of habitat loss and ecosystem destruction (Til- man et al., 2002). Clearance for cropland or permanent pasture has already reduced the extent of natural habitats on agriculturally usable land by more than 50% (Green et al 2005), and much of the rest has been altered by temporary grazing (Groombridge and Jenkins, 2002). Habitat modification already affects more than 80% of globally threat- ened mammals, birds and plants (Groombridge and Jenkins, 2002), with implications for ecosystem services and human well-being. Of the world’s land, cosatal and ocean area, only 13%, 6% and less than 1%, respectively, are within protcted areas (WDPA, 2010).
Despite its crucial role for providing ecosystem services agricul- ture remains the largest driver of genetic erosion, species loss and conversion of natural habitats (MA, 2005). Globally over 4,000 assessed plant and animal species are threatened by agricultural intensification (IUCN, 2008). A central component in avoiding loss of biodiversity and ecosystem services, such as water, from ex- panding agricultural production and resource extraction is to limit the trade-off between economic growth and biodiversity by stimu- lating to agricultural productivity and more efficient land use.
Most global scenarios project increased use of land for arable crops and grazing. Scenarios from the Global Environmental Outlook, The Millennium Assessment and the Global Biodi- versity Outlook all show increases of land use as a result of a growing population and increased economic development.
Further enhancement of agricultural productivity (‘closing the yield gap’) and reduction of post harvest losses are key factors in reducing the increased need for land and, consequently, the rate of biodiversity loss (CBD, 2008). These options should be implemented carefully in order not to cause new undesired negative effects, such as emissions of nutrients and pesticides,
as well as risks of land degradation. An increase in protected areas and change towards more eco-agricultural cropping sys- tems and sustainable meat production could have immediate positive effects on both biodiversity and water resource man- agement, while increasing revenues from tourism.
A reduction of crop- and pasture land can only be achieved if dras- tic changes in diets are assumed. Some of these more extreme scenarios are presented by Wise et al. (2009) and Stehfest et al., (2009). They suggest that if enhanced agricultural productivity is assumed and the consumption of meat is greatly reduced then large areas will become available for forest and natural grassland recovery. Some scenarios also predict a shift of agricultural pro- duction towards different regions, resulting in a reduction of ag- ricultural land in, for example, Europe. Recovery of biodiversity is possible on abandoned land, but the rate and quality depend on actions taken on these lands. In models like GLOBIO this factor is not yet incorporated at this stage. Autonomous recov- ery is a slow process and is represented by the land use category ‘secondary forest’ in GLOBIO (Alkemade et al., 2009). Restora- tion activities for example plantations may speed up the recovery process, but are not included in the GLOBIO model.
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