Biodiversity is a key measure of the “health” of life on Earth. During mass extinction events, biodiversity of both plants and animals bottoms out. Man-made climate change is currently contributing to the world’s sixth mass extinction event, a natural disaster caused entirely by detrimental human activity. A new study, led by researchers at the University of Minnesota, reaffirms the importance of biodiversity: it can help protect ecosystems from extreme climatic conditions.
The rate at which humans are changing the climate is unprecedented, with dramatic atmospheric, continental and oceanic warming catching life on Earth off-guard. Biodiversity – the variety of species in a given ecosystem – is being reduced in every one of the world’s biomes, regions of the world with similar climates.
The study, published in Nature, examined the biodiversity of 46 grasslands in North America and Europe. The researchers investigated how areas with different levels of plant biodiversity affected the overall rate of each area’s primary production – a measure of the amount of organic material (for example, glucose) that is produced during photosynthesis.
The range of climatic seasons each grassland experienced was rated on a scale of one to five, from extremely dry to extremely wet. The primary productivity of each area was measured in terms of the amount of above-ground plant material that grew each year. The mass of vegetation that a plant produces is directly related to how much organic material the plant produces during photosynthesis. This primary productivity index – known as biomass – can apply to an entire community of plants, and this is precisely what was calculated for each individual area over an annual period.
At the beginning of the study, the researchers manipulated the plant biodiversity of the grasslands by removing a range of plants from each area. This gave them the opportunity to compare and contrast the effects of this at the end of the extensive experiment.
Using this large selection of variously manipulated grasslands, the team found that areas with particularly high plant biodiversity had stable levels of primary productivity during both wet and dry climate events. Overall, the primary productivity of plant communities with a very low biodiversity – areas containing just one or two species – changed on average by 50% during the extreme climate events. On the other hand, those with 16 to 32 plant species changed by only 25%.
Although areas with high biodiversity proved to be better buffers against rapidly changing, harsh climatic events, the researchers found that the level of an area’s biodiversity did not seem to strongly influence how quickly a site eventually returned to normal levels of productivity.
So it seems that the initial resistance to change, rather than the area’s response to dramatic climate change, is the major mechanism through which biodiversity protects a community’s production and stability in times of rapid change.
A recent report on the biodiversity of the world’s oceans has cast an incredibly gloomy shadow over their future: many key species in a variety of marine ecosystems are doomed to die out. Clearly, without biodiversity, the world’s ecosystems are left exposed to the devastating climatic changes that humans are responsible for.