Monday, August 29, 2016

Imbalance of nutrients threatens biodiversity

Niche dimensionality provides a general theoretical explanation for biodiversity—more niches, defined by more limiting factors, allow for more ways that species can coexist. Because plant species compete for the same set of limiting resources, theory predicts that addition of a limiting resource eliminates potential trade-offs, reducing the number of species that can coexist. Multiple nutrient limitation of plant production is common and therefore fertilization may reduce diversity by reducing the number or dimensionality of belowground limiting factors. At the same time, nutrient addition, by increasing biomass, should ultimately shift competition from belowground nutrients towards a one-dimensional competitive trade-off for light.

In his description of an entangled bank of species, Charles Darwin illustrated the principle that species must manage complex interdependencies to successfully coexist in natural communities. His theory explains the mechanism of how a number of species should be competing for resources when they are actually coexisting because of the subtle differences in their resource needs.

The Nutrient Network, a global network of researchers now tested the impact increased nutrient levels are having on grasslands across six continents. The experiment was conducted across 45 grassland sites.

What the colleagues found, was that if you change the limiting resources and add an abundance of resources such as nutrients like phosphorus, nitrogen and potassium, it will lead to a favouring of some species over others because competition is then shifted above ground for light. This will in turn evoke competition between species, leading to one species dominating the land area.

Undoubtedly, the human influence on the nutrient cycle through greater globalisation, has a damaging effect on ecosystem biodiversity. Unfortunately, many of the ecosystem functions that humans need to survive, such as oxygen production, water filtration, nutrient cycling, pollination, and carbon sequestration, are provided by richly diverse ecosystems.

The loss of diversity was not driven by the addition of any single added resource for example nitrogen or potassium, we found greatest diversity loss occurred with the addition of a combination of two or more resources.Simply put, the more nutrients, the less biodiversity. What this research does is provide tangible evidence that global change is driving environmental conditions beyond our planetary boundaries.

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