Biodiversity and human-caused environmental change

Biodiversity

The human-caused change that is the greatest threat to biodiversity is anthropogenic climate change, which is caused by the burning of fossil fuels. This will create massive climate change, affecting the habitats where species live, causing significant issues that could affect their future survival, if they cannot adapt. This paper focuses on how these changes will affect biodiversity at the ecosystem level. The authors choose this focus because the ecosystem is a set of related entities -- individual species, for example -- but their interrelation is critical. If climate change affects a single species, it could disrupt the entire ecosystem even if the other species are not affected by the climate change. This example highlights the destructive capabilities of climate change.

One of the main points that the authors make is that a single species can and does affect an entire ecosystem. They discuss the removal of a single species, such as when the sea otter was hunted in Russia, leading to an explosion of sea urchins, which were the otters' main prey. Ecosystems exist in a state of delicate balance, so any individual species can have a significant impact on that balance.

The paper describes some outcomes as trophic cascades. The sea otter example is one. A single species, the sea otter, was removed from the ecosystem, but the cascade affected a far greater number of species. Sea urchins proliferated, and they would have crowded out competitor species, and whatever the urchins eat would have been depleted as well. This is an example of trophic cascade that was described in the paper.

Biodiversity also prevents invasion. Biodiversity is something that makes it more difficult for species to enter an ecosystem and succeed. When the ecosystem is in balance, it is less likely that an outside species can find a niche, when there are no available niches in a balanced ecosystem. An invasion species is generally thought to be more likely to flourish if there are available niches in an ecosystem. Alternations to biodiversity have had a negative impact on society. A good example can be found with the passenger pigeon. This bird outcompeted mice that carried the tick that transmitted Lyme disease. When humans killed off the passenger pigeon, those mice were able to flourish, so the ticks did as well, and Lyme disease today is a much bigger problem than it was when the passenger pigeon existed.

2. Researchers started to investigate the effects of biodiversity loss in the 1980s when concerns about the rate at which species were being lost escalate to concerns about the "structure and functioning of whole ecosystems." BEF is "biodiversity and ecosystem functioning," while BES is "biodiversity and ecosystem services." The former is about the function of biodiversity, the latter specific to how it can help people.

The six consensus statements are that biodiversity loss "reduces the efficiency by which the ecological communities capture essential resources" -- that biodiversity loss is harmful to ecosystems. Biodiversity increases the stability of ecosystems over time, for example defending against invaders. Change accelerates as biodiversity loss increases, and that this is the nature of biodiversity loss. The fourth statement is "diverse communities are more productive, while statement five is that "loss of diversity at trophic levels has the potential to influence ecosystem functions" and that "functional traits of organisms have large impacts on the magnitude of ecosystem functions," implying that outcomes of loss of diversity are incredibly varied and therefore difficult to predict.

The four emerging trends are that biodiversity loss is as powerful as other change drivers, that diversity effects grow stronger over time, that maintaining multiple ecosystem processes requires higher levels of biodiversity, and that the consequences of biodiversity loss can be predicted from evolutionary history.