What conservationists need to know about farming - PubMed (original) (raw)

What conservationists need to know about farming

Andrew Balmford et al. Proc Biol Sci. 2012.

Abstract

Farming is the basis of our civilization yet is more damaging to wild nature than any other sector of human activity. Here, we propose that in order to limit its impact into the future, conservation researchers and practitioners need to address several big topics--about the scale of future demand, about which crops and livestock to study, about whether low-yield or high-yield farming has the potential to be least harmful to nature, about the environmental performance of new and existing farming methods, and about the measures needed to enable promising approaches and techniques to deliver on their potential. Tackling these issues requires conservationists to explore the many consequences that decisions about agriculture have beyond the farm, to think broadly and imaginatively about the scale and scope of what is required to halt biodiversity loss, and to be brave enough to test and when necessary support counterintuitive measures.

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Figures

Figure 1.

Figure 1.

The relationship between per capita demand for crop calories and per capita gross domestic product (GDP) from 1961 to 2003, for groups of countries ordered from richest (A) to poorest (G). The curve is fitted to the square root of per capita GDP. From Tilman et al. [14].

Figure 2.

Figure 2.

An indication of the relative number of papers in the conservation literature (blue bars; number of relevant papers) that address the biodiversity impacts of specific crops, based on a random sample of 20% of 1062 papers returned from a literature search. Also shown are the global harvested area in 2010 (red; area in 106 ha) and mean annual increment in area (green: expansion; 104 ha) based on linear regression of area from 1999 to 2010 [35]. The 10 crops on the left are the top 10 crops by harvested area, and the five on the right are additional crops noted for their biodiversity impact. The top 10 crops by annual increment is similar except that oil palm, sugar cane, vegetables and sunflower replace barley, sorghum, millet and cotton. The literature search was carried out in February 2012 on Web of Knowledge for papers published up to 2011 in 14 conservation journals, with search terms for crop names and for farmland*, arable* or cereal* entered in the topic field (which searches title, abstract and key words). Papers were counted if they were relevant to the impact on biodiversity of the extent or management of named crops; those focused only on conservation of crop genetic diversity, pest control or human–wildlife conflict were excluded.

Figure 3.

Figure 3.

(a) Estimated annual greenhouse gas emissions from agriculture between 1961 and 2005 assuming observed increases in yield, per capita demand and population (RW) and (b) two alternative world scenarios in which yield remained at 1961 levels but per capita demand grew as in RW (AW1) or (c) both yield and per capita demand were unchanged from 1961 (AW2). The dotted lines represent uncertainty (±20%) in the change in carbon stock owing to land conversion. Note the logarithmic _y_-axis. From Burney et al. [70].

Figure 4.

Figure 4.

Mean (±s.e.) maize yield in monocrop plots (open bars) and push–pull plots (filled bars) in different districts of western Kenya. Means are from 30 fields and three growing seasons in each district, and in every district differ between monocrop and push–pull plots at p < 0.0001. From Khan et al. [82].

Figure 5.

Figure 5.

Schematic summarizing what some ‘biodiversity-friendly’ certification schemes currently endorse (a) compared with landscapes that involve land sparing within large farms (b) or across a group of farms (c). In each landscape, the same total area (denoted by the green shapes) is given over to wild nature, but recent evidence suggests that its value for other species and for ecosystem services might increase from left to right, raising the question of whether certification could be realigned towards incentivizing high-yield farmers to collectively set aside adjacent areas of land for conservation. Developed from ideas in Edwards et al. [92] and Komar [97].

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