Biodiversity Patterns in Agricultural Systems

by

Les Firbank, Sofia Biffi

• LAST REVIEWED: 26 July 2017
• LAST MODIFIED: 26 July 2017
• DOI: 10.1093/obo/9780199830060-0183

Introduction

Biodiversity is declining at a global scale due to large and small scale processes associated with agricultural practices. Agriculture involves transforming natural habitats into systems designed to promote certain species for our consumption. The scale of this transformation is huge; it is estimated that 25 percent of potential net primary production is currently appropriated for human use, a figure that could nearly double by 2050. Inevitably, this appropriation reduces the amount of energy available for all other taxa, with inevitable consequences for biodiversity. These consequences are not uniform or random, however, because agricultural systems involve the reconfiguration of habitats and landscape elements, creating niches that allow some non-cropped species to survive, and even thrive in agricultural systems, depending on the traits they possess. Agricultural landscapes can be very biodiverse, and of high social and cultural value, especially where there has been continuity of management over long periods of time and the managed landscape presents natural habitat patches. The matrix of natural, semi-natural, and managed landscape plays a major role in supporting biodiversity by creating a complex spatial pattern of ecosystems and habitats. In many parts of the world this management continuity is under threat from land abandonment on the one hand and intensification on the other; both may cause biodiversity loss. However, it is being increasingly recognized that some non-cropped taxa perform valuable benefits to agricultural production, giving rise to the idea that agricultural landscapes may be redesigned to enhance such ecosystem services. The outcomes of such redesign may therefore still be biodiverse, but different to what is found now.

History

Agricultural landscapes are often cultural in origin, and they have been managed for hundreds or thousands of years. Farmed and forested landscapes can provide suitable conditions for high levels of biodiversity. In the early 20th century, ecologists started to describe the vegetation and birds in relation to habitats (including grassland and arable), themselves a function of soil, climate, and management (Tansley 1939). However, these farmed habitats were becoming increasingly modified and homogenized because of changes to land management. Repeated surveys of plants and birds (especially) revealed declines of biodiversity on agricultural land that can be traced to different aspects of agricultural intensification and expansion (Donald, et al. 2001; Koh and Wilcove 2008). As farmland became the subject of conservation measures (at least in Europe), resolving the mechanisms of these declines became important, with the elucidation of the indirect effect of pesticides on grey partridge numbers (Rands 1985) being particularly influential. The role of landscape complexity in supporting those taxa that required combinations of habitat (especially some birds) or that used linear and other features to persist in agricultural landscapes, as studied using metapopulation dynamic approaches (see Oxford Bibliographies articles “Landscape Ecology” and “Metapopulations and Spatial Population Processes”). The question of whether biodiversity is best conserved on land used for farming (land sharing), or on land spared from agriculture (land sparing), was raised and remains contested (Green, et al. 2005). Habitat loss to agriculture together with climate change today represent the major threats to biodiversity and may severely affect biodiversity in the coming decades (Jetz, et al. 2007). In many other parts of the world, the loss of biodiversity on farmland is less of a conservation concern than a risk to certain ecosystem functions that support farming, especially in the absence of chemical interventions (Altieri 1999). One response is ecoagriculture, which seeks to design new agricultural landscapes that are both biodiverse and productive (Scherr and McNeely 2008). Concerns about loss of ecosystem services on farmland are now global (Potts, et al. 2010), and increasingly researchers are seeking to establish the roles of less charismatic taxa, especially those in the soil (Delgado-Baquerizo, et al. 2016).

• Altieri, M. A. 1999. The ecological role of biodiversity in agroecosystems. Agriculture Ecosystems & Environment 74.1–3: 19–31.

  DOI: 10.1016/S0167-8809(99)00028-6

  This paper established that on-farm biodiversity has an active role in supporting sustainable food production.

• Delgado-Baquerizo, M., F. T. Maestre, P. B. Reid, et al. 2016. Microbial diversity drives multifunctionality in terrestrial ecosystems. Nature Communications 7.

  DOI: 10.1038/ncomms10541

  No single classic paper yet is available on the importance of below ground biodiversity on agricultural production. This paper gives evidence that soil microbial biodiversity positively relates to multifunctionality in terrestrial ecosystems.

• Donald, P. F., R. E. Green, and M. F. Heath. 2001. Agricultural intensification and the collapse of Europe’s farmland bird populations. Proceedings of the Royal Society B: Biological Sciences 268.1462: 25–29.

  DOI: 10.1098/rspb.2000.1325

  This is one of several papers in which the authors analyze data on farmland birds in relation to different aspects of agricultural change to help support conservation policy.

• Firbank, L. G., S. Petit, S. Smart, A. Blain, and R. J. Fuller. 2008. Assessing the impacts of agricultural intensification on biodiversity: A British perspective. Philosophical Transactions of the Royal Society B: Biological Sciences 363.1492: 777–787.

  DOI: 10.1098/rstb.2007.2183

  This is a national-scale study showing that plant diversity was a function of both field and landscape-scale variables, while bird species richness was a function of landscape-scale variables only.

• Green, R. E., S. J. Cornell, J. P. W. Scharlemann, and A. Balmford. 2005. Farming and the fate of wild nature. Science 307.5709: 550–555.

  DOI: 10.1126/science.1106049

  This paper opened up the land-sharing land-sparing debate about biodiversity and agriculture. While the approach followed a simple model of potential trade-offs, the paper proved influential in stimulating thinking and provoking a discussion that remains a rich one and that engages the agricultural industry.

• Jetz, W., D. S. Wilcove, and A. P. Dobson. 2007. Projected impacts of climate and land-use change on the global diversity of birds. PLoS Biol 5:e157.

  DOI: 10.1371/journal.pbio.0050157

  This paper projected four Millennium Ecosystem Assessment scenarios integrating land-use and climate changes to create a global assessment of bird species loss. This study assumes stationary geographic ranges; thus, it may overestimate the biodiversity loss.

• Koh, L. P., and D. S. Wilcove. 2008. Is oil palm agriculture really destroying tropical biodiversity? Conservation Letters 1.2: 60–64.

  DOI: 10.1111/j.1755-263X.2008.00011.x

  The authors analyze the loss of bird and butterfly biodiversity associated with oil palm expansion in primary and logged forest in Malaysia.

• Potts, S. G., J. C. Biesmeijer, C. Kremen, P. Neumann, O. Schweiger, and E. Kunin. 2010. Global pollinator declines: Trends, impacts and drivers. Trends in Ecology & Evolution 25.6: 345–353.

  DOI: 10.1016/j.tree.2010.01.007

  The authors reviewed data to bring to global attention pollinator declines and their potential impact on crop production.

• Rands, M. R. W. 1985. Pesticide use on cereals and the survival of grey partridge chicks: A field experiment. Journal of Applied Ecology 22.1: 49–54.

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  This is a simple but classic field experiment of how partridge survival is lower if herbicides are used, because of reductions in invertebrate prey. The risk of such indirect effects of land management formed the basis for assessing the ecological effects of GM crops in the United Kingdom.

• Scherr, S. J., and J. A. McNeely. 2008. Biodiversity conservation and agricultural sustainability: Towards a new paradigm of “ecoagriculture” landscapes. Philosophical Transactions of the Royal Society B: Biological Sciences 363.1491: 477–494.

  DOI: 10.1098/rstb.2007.2165

  This paper proposes that biodiversity is actively managed to create new biodiversity and productive farming systems.

• Tansley, A. G. 1939. The British islands and their vegetation. Cambridge, UK: Cambridge Univ. Press.

  A classic text describing an early descriptive approach to British vegetation.