This paper, by Phalan et al, provides a global overview of patterns of crop expansion in relation to conservation priorities in tropical countries. It seeks to address the following questions:
- Which crops cover most area in tropical countries and tropical biomes?
- In which tropical countries has most expansion occurred in recent years, and which crops were involved?
- How are remaining areas of cultivation potential distributed across tropical countries, particularly in relation to priority areas for biodiversity conservation?
The focus is on tropical countries because they support the highest concentrations of species richness and endemism for most well-studied taxonomic groups, have large projected increases in demand for food from human populations growing in size and wealth, are experiencing high rates of habitat loss, and are seen as providing the most scope for increasing global agricultural production. The paper does not consider other forms of land use, such as livestock grazing, forestry and residential and commercial development. It notes that conversion to cattle pasture remains the dominant driver of deforestation in Latin America, where over three-fifths of recent global humid forest conversion has occurred but focuses on cropland expansion because it changes habitat structure so profoundly, can be more accurately assessed by remote sensing (compared to many forms of grazing and forestry) and is so extensive (compared to urban areas).
Abstract is as follows
Expansion of cropland in tropical countries is one of the principal causes of biodiversity loss, and threatens to undermine progress towards meeting the Aichi Biodiversity Targets. To understand this threat better, we analysed data on crop distribution and expansion in 128 tropical countries, assessed changes in area of the main crops and mapped overlaps between conservation priorities and cultivation potential. Rice was the single crop grown over the largest area, especially in tropical forest biomes. Cropland in tropical countries expanded by c. 48,000 km2 per year from 1999–2008. The countries which added the greatest area of new cropland were Nigeria, Indonesia, Ethiopia, Sudan and Brazil. Soybeans and maize are the crops which expanded most in absolute area. Other crops with large increases included rice, sorghum, oil palm, beans, sugar cane, cow peas, wheat and cassava. Areas of high cultivation potential—while bearing in mind that political and socio-economic conditions can be as influential as biophysical ones—may be vulnerable to conversion in the future. These include some priority areas for biodiversity conservation in tropical countries (e.g., Frontier Forests and High Biodiversity Wilderness Areas), which have previously been identified as having ‘low vulnerability’, in particular in central Africa and northern Australia. There are also many other smaller areas which are important for biodiversity and which have high cultivation potential (e.g., in the fringes of the Amazon basin, in the Paraguayan Chaco, and in the savanna woodlands of the Sahel and East Africa). We highlight the urgent need for more effective sustainability standards and policies addressing both production and consumption of tropical commodities, including robust land-use planning in agricultural frontiers, establishment of new protected areas or REDD+ projects in places agriculture has not yet reached, and reduction or elimination of incentives for land-demanding bioenergy feedstocks.
The paper concludes by making a number of policy recommendations. In order to halt further habitat loss, yields will need to be increased where potential exists to do this without negative environmental impacts. Nation-level land use policies will need to be developed or enforced to stabilise the agricultural frontier around the last big blocks of wilderness through appropriate strategic land-use planning, infrastructure planning, better regulation of large international land acquisitions, and protected area designation. It also highlights the potential of voluntary certification and other market-based initiatives to help reduce the impact of agriculture although notes that this potential has been realised to only a limited extent to date and that the scope of such schemes is limited given the scale of land use planning required. Hence the need for government intervention. It also points out that biodiversity protection will be easier to achieve if global consumption of agricultural products can be reduced or stabilised. In the developed world, there is considerable scope to eliminate over-consumption, promote diets which are less land-demanding and reduce post-consumer waste. Reforming incentives for bioenergy to support only those feedstocks not implicated in direct or indirect land-use change could help to reduce global demand for agricultural land. In the developing world, the most important issues include rising meat consumption by an emerging middle class, rapid population growth and post-harvest losses. Some of these issues can only be addressed by national and international policy, while others can be addressed at a local level, for example by NGOs.
Citation as follows
Phalan B, Bertzky M, Butchart SHM, Donald PF, Scharlemann JPW, et al., 2013, Crop Expansion and Conservation Priorities in Tropical Countries. PLoS ONE
You can read the open access article here. For an interview on agroforestry to which Ben Phalan, one of the paper’s authors contributed, see here. For a paper by Phalan et al on the ‘land sparing versus land sharing’ debate on biodiversity protection, see here. You might also be interested in our resources on land-use and ecosystems here.