How does biodiversity affect the farm ecosystem?

Summary

The practical message from this study is that it is prudent for a land manager to retain as many species as possible. Because most species in farmland occur in the soil, the quality of the soil is paramount in maintaining biodiversity.

Research findings

It has often been debated whether each species present in an ecosystem is essential for effective functioning of that ecosystem. The extreme view is that redundancy is common, and that the loss of some species should not have any prominent effect on the working of an ecosystem. According to this this viewpoint, a process influenced by a deleted (locally extinct) species is taken over by another species.

This paper challenged this view, based on experiments conducted in pasture in Europe in a study called Project BIODEPTH. This study examined 7 ecosystem processes or properties:

• wood decomposition
• cotton decomposition
• light at ground level
• below-ground biomass
• above-ground biomass
• unconsumed soil nitrogen
• above-ground nitrogen pool

The study found, after a complex statistical analysis, that the 7 ecosystem processes were not affected by exactly the same species. Because different species affect different processes, maintaining ‘multifunctional’ ecosystems requires greater diversity than was previously suggested by studies that examined single ecosystem processes in isolation.

These findings lend support to a popular viewpoint known as the ‘insurance’ hypothesis. This hypothesis states that.... “biodiversity has an insurance value through buffering processes at the ecosystem-level in a way similar to a diverse investment portfolio, in which financial risk is spread and average performance is improved in the long (instead of short) term.”

The practical message from this study is that it is prudent for a land manager to retain as many species as possible. As most species in farmland will occur in the soil, therefore, the quality of the soil is paramount in maintaining biodiversity.

Reference

Hector A & Bagchi R (2007) Biodiversity and ecosystem multifunctionality. Nature 448: 188-190. Read Abstract.
 

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