5.4.1 Cropping and Crop Harvesting Practices

There are a variety of aspects of cropping and crop harvesting practices regarding terrestrial biofuels that may impact biodiversity. The use of cropping systems which include a relatively wide crop genetic diversity may allow for more services in the fields of pest control and pollination than cropping systems that have a narrow ge­netic base (Tilman et al. 2006; Hajjar et al. 2008). And annual cropping systems that use cover crops may well be better in soil conservation than cropping systems that do not use such crops (Jarecki and Lal 2003). There may also be differences in the non-crop biodiversity of production systems. For instance, extensively managed perennial grass crops (e. g. Miscanthus, switchgrass, mixtures of prairie grasses) may allow for more invertebrate diversity than intensively managed annual crops, and willow coppice plantations may benefit some bird species (Anderson and Fergus- son 2006). Replacement of extensively used grasslands by arable land for biofuel cropping may negatively affect bird species that rely on such grassland habitats (e. g. Schleupner and Link 2008). Sage et al. (2006) compared bird populations in a short rotation willow coppice, used for biofuel production, and other arable crops in England and concluded that it was unlikely that the planting of willow coppice on unimproved farmland would lead to a conservation gain. However, planting willows in small blocks of different age classes and no harvest in summer would, in their view, benefit bird populations in short rotation willow coppice fields.

One likely future development to which increased transport biofuel production will contribute is intensification of agriculture (Goldemberg 2008; Searchinger et al. 2008; Sukhdev 2008). Intensified agriculture has a variety of effects on living nature. Higher production may provide more resources for a number of mammals, birds and insects. For instance, populations of bumblebees may increase in landscapes with intensive rapeseed cropping (Tscharntke et al. 2005). On the other hand, high inten­sities of nutrient and pesticide use tend to reduce biodiversity (Tilman et al. 2001a; Ptacnik et al. 2008). Intensification of agriculture may also decrease edge habitats such as hedges (Tscharntke et al. 2005). Intensified agriculture is furthermore often associated with lowering water tables (Tscharntke et al. 2005), and this may lead to changes in biodiversity. Also, increased irrigation, which is expected to contribute to intensified agriculture, is likely to have an impact on biodiversity by lowering the

availability of water to natural species. This is exemplified by the negative impact of increased irrigation on biodiversity and ecosystem services of wetlands and rivers in the European Union, the United States, China and Australia (Gerakis and Kalburtji 1998; Gleick 2003; Castaneda and Herrero 2008; Postel 2008). On average, the net effect of intensified agriculture is a decline in biodiversity among many different taxa (Liira et al. 2008). Such a decline may have a rebound effect on crop produc­tivity. For instance, it has been found that crop pollination from native bees may be at risk from agricultural intensification (Kremen et al. 2002).

Handling harvest residues may also matter to biodiversity. There are bird species which depend to at least some extent on harvest residues. Well known is the depen­dence of waterfowl on residues from harvesting in flooded rice fields (van Diepen et al. 2004), the consumption of harvest residues in the Mississippi delta by water­fowl (Gallagher et al. 2003) and the dependence of cranes on residues from corn harvesting in Northern Germany. Residue removal for biofuel production would in such cases reduce bird populations. In some cases, this may have knock-on effects. For instance, in rice-growing areas, waterfowl dependent on residues may be im­portant in maintaining productivity as they reduce weed pressure and pests and in­crease N cycling (Bird et al. 2000; van Diepen et al. 2004), and they may also serve as a food source. There is little information about the impact on living nature of the cultivation of algae. Open water seaweed farming near the coast of Zanzibar has, however, been found to be associated with less sea grass and reduced abundance and biomass of macrofauna (Eklof et al. 2005).