Feature Image: Photo credit: https://pixabay.com/photos/farmer-tractor-agriculture-farm-880567/
Source Article: Beckmann, N., Gerstner, K., Akin-Faiyge, M., Ceauşu, S., Kambach, S., Kinlock, N.L., Phillips, H.R.P., Verhagen, W., Gurevitch, J., Klotz, S., Newbold, T., Verburg, P.H., Winter, M., Seppelt, R., 2019. Conventional land-use intensification reduces species richness and increases production: A global meta-analysis. Global Change Biology, 25: 1941-1956. https://doi.org/10.1111/gcb.14606
Biodiversity is under threat
Biodiversity is the variety of different life forms on Earth. A common way of measuring biodiversity is to count the number of different species in a given area, known as the species richness. Biodiversity is important because each species serves a different role in an ecosystem and having a large collection of different species means the ecosystem is healthier. Ecosystems with more biodiversity are also more resilient to disturbance. This is because when many species face a disturbance, there is a higher probability that some of them will survive.
But the biodiversity of our planet is under threat. A recent report from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services states that over a million species of plants and animals are currently threatened with extinction. The report further states that the rates of species decline globally are unprecedented in human history. For more information on the reports findings, you can check out this summary or read regional assessments.
Agricultural production must increase
At the same time that our planetary species losses are increasing, so too is the human population. In fact, the United Nations estimates that there will be 9.8 billion humans occupying the planet Earth by 2050 and 11.2 by 2100. Providing food for our increasing human populations means that the production of agriculture will have to increase worldwide.
There are several ways to increase the production of foods. The first option is to increase the amount of land used for farming. However, converting areas such as forests into farmland has a major negative impact on the ecosystem and has been shown to decrease biodiversity. The second option is to increase crop production on existing farms through a process called intensification. Conventional intensification describes an increase in farming inputs (e.g. fertilizer, machinery, labor, harvesting, animal density) in an effort to increase the output, which is the amount of crop or livestock produced.
What is the relationship between conventional agricultural intensification, crop production, and species richness?
Michael Beckmann of the Helmholtz Centre for Environmental Research and his colleagues recently published a study where the analyzed previously published scientific research to determine the impacts of conventional agriculture on crop production and species richness, or the number of species. Beckmann and his colleagues were especially interested in studies that reported both production and species richness data in the same area. They found 115 studies from across the world that covered 449 cases in three different agricultural systems: crop, fodder (e.g. crops for livestock), and wood production. Each case was classified by intensity, ranging from low to medium to high. The researchers were especially interested in understanding how crop production and species richness changed when systems increase agricultural intensification. Low intensity farms typically had no fertilizer, biological pest control, or low density grazing, medium intensity farms had target pesticides, single harvests each year, or medium density grazing, and high intensity farms had non-targeted pesticides, multiple harvests each year, or high density grazing.
Beckmann and his colleagues found that there was generally a trade-off between crop production and species richness when farming methods were intensified. Across all production systems, they reported an average increase of 20% in crop yield, but this was accompanied by an average loss of 9% of species richness in the area. When analyzing the data further, however, they discovered that there were cases when crop yield increased with no significant impact on species richness, such as within high intensity farms. This was not true in all cases. For example, when farming efforts were intensified on medium intensity farms, crop yield was increased up to 85%, but species richness declined by 23%.
Overall, Beckmann and his colleagues concluded that there is a trade-off between increasing production and maintaining biodiversity on many farms, although they did find some examples were the trade-off was minimized. More than anything, there results suggest that it is important for future research to measure both crop yield and biodiversity on the same farms, especially when farming efforts are being intensified. Ideally, additional research can identify specific cases where crop yield can be increased to feed the growing human populations, while at the same time conserving the biodiversity that drives healthy ecosystems.