No Correlation Between Yield Production and Biodiversity in Large-Scale Farming

There is a growing concern about the amount of food being produced and the growth of the human population. In an effort to meet the demands of population growth it is feared that many natural habitats will have to be replaced by agricultural land. This would be hugely detrimental to biodiversity, especially in tropical regions, which are home to most of the world’s biodiversity and 13% of human agriculture. Although more wildlife-friendly agriculture practices have been put forward, they are rarely used on a large scale because it is believed they decrease the total yield. Clough et al. (2011) explore this argument in Indonesian cocoa agroforestry plantations. They discovered that there is no correlation between biodiversity and agricultural yield, opening up many possibilities in large-scale wildlife friendly agricultural practices. They also explored possible ways to benefit yield and biodiversity in trees and birds, giving an example for a new way of thinking about farming and biodiversity conservation. While their findings do not suggest that wildlife friendly farming practices will end the depletion in biodiversity, as primary forests still are home to many more species than any other area on earth, it is a step forward as we attempt to feed our growing population and conserve the planet and the other species on it. –Mathew Harreld
Clough, Y., Barkmann, J., Juhrbandt, J., Kessler, M., Wanger, T.C., Anshary, A., Buchori, D., Cicuzza, D., Darras, K., Putra, D.D., Erasmi., S., Pitopang, R., Schmidt, C., Schulze, C.H., Seidel, D., Steffan-Dewenter, I., Stenchly, K., Vidal, S., Weist, M., Wielgoss, A.C., Tscharntke, T. 2011. Combining high biodiversity with high yields in tropical agroforests. PNAS 108:20, 8311–8316.

       The importance of food and agriculture in our culture is unquestionable, and the global importance of agriculture will continue to grow in the years to come. As human populations grow there is an increasing demand for food. Agriculture, however, is one of the main threats to global biodiversity. As farms try to increase yields to meet increasing demands, removing natural habitats and increasing farmland is often the action taken. If wild species are to survive then a balance must be found between agriculture and biodiversity. There is the potential for biodiversity-friendly farming. This farming method is often criticized for decreasing the yield quantity because of the focus on biodiversity preservation. Clough et al. explore this argument in Indonesian cacao farms. The argument that wildlife friendly farming practices is ineffective on larger scales is put to the test. The authors evaluated the possibility of combining high species diversity and high yields and where this might be done.
       The authors chose to focus on tropical regions in Indonesia because of the high biodiversity combined with the high human populations density. Furthermore, agriculture in tropic regions compasses 13% of the total agricultural system globally, and thus is an important area for future agricultural output.
       Clough et al. broke the study into two parts: a field study and a survey study. The field study consisted of data collected on yield and species richness in nine different taxonomic groups, during a two-year period. The authors used the land of 43 smallholder cacao agroforestry system in Sulawesi, Indonesia. Only mature plots ten to twenty years old were chosen for the study. Also, the authors studied the possible relationship between biodiversity and yield as distance to a natural forest changed.
       The survey portion of the study focused on 60 cacao plantations that were run only by the owners, and were not affected by the study. Only tree species were used as a measurement of biodiversity, however other agronomic data were recorded. These data were used mostly for a better understanding of general yield patterns throughout the regions.
       The authors discovered a surprising result once their data were collected, there was little to no correlation between species richness and yield. This general lack of correlation could potentially have large impacts on farming methods, but first the authors explored what does affect species richness and yield.
       They found that differences in region and altitude had large impacts on species richness, but it was mainly associated with distance from forests and shade by trees. There was a clear negative relationship between distance from forest and species richness. Plots with high levels of trees and shade had more bird species, but had fewer light-dependent species, such as herbs and butterflies.
       Yield was mainly negatively affected by the amount of shade a plot received, however distance to forest had a small positive effect. Other variables proved to have little effect on yield. Through the survey portion of the study, it was determined that labor and pesticide use were the largest determinants of yield.
       In an attempt to find a possible method of sustaining high yields and high biodiversity the authors focused on the effects of trees, yield, and birds. They found that birds were more dependent on tree height than total amount of shade, whereas yield was affected by shade. Therefore it may be possible to increase bird habitat with taller, but fewer trees, resulting in less shade.
          This study reveals that it is possible to have wildlife friendly farms that produce high yields. These findings suggest that wildlife friendly policies can be, and should be, implemented in agriculture without fear of yield loss. The authors also caution that their findings may be inaccurate because there may be a lag in time between the presence of farms and their effect on biodiversity. This is why the authors chose the most established and mature agroforestry sites. More data need to be collected to continue to record the effects on the practices of wildlife friendly agricultural on biodiversity and yield. At first glance, though, the findings of Clough et al. are quite stunning and exciting, leaving the potential for new wildlife friendly farming practices that produce high yields for a growing human population.

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