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Disruptions to ecosystems can rapidly change niche availability and thus the ability of organisms to survive. A niche is the role a species plays in an ecosystem. This includes how it obtains food and shelter, how it reproduces, and how it interacts with other organisms. Disruptions to the environment can remove aspects of this that prevent the species from filling the niche it evolved to fill. If these disruptions are large enough, they can even change the local and global distribution of ecosystems. This can have a dramatic effect on how all organisms live in a given area.
Invasive Species
The introduction of an invasive species to an ecosystem can dramatically affect a community and the ecosystem dynamics. An invasive species is an organism, not native to the ecosystem, that typically can spread rapidly and outcompete native species for resources. Since these species are not native, they often lack predators that would normally control their populations. This allows them to multiply and disrupt the ecosystem. Since their population is unchecked, they can lead to the extirpation of other species within the community.
Human Impact
Humans have a massive impact on the environment, with the most obvious being habitat destruction and change. As society has developed, humans have enacted widespread land conversion, changing natural areas to ones dominated by buildings and concrete or agricultural production. This removal of the natural ecosystems removes areas for species to inhabit and thrive. Humans also introduce new diseases that can devastate native species. Chytrid fungus, for example, is a pathogen that kills amphibians by disrupting their skin function. Humans have spread this disease across the world to new areas where native frogs have no resistance to the fungus. Humans are also often the mechanism by which invasive species enter new communities.
Humans have also developed ways to use chemicals to increase the production and efficiency of agriculture. These chemicals, in the form of fertilizers, pesticides, and herbicides, can have a negative impact on the environment. Eutrophication occurs when a body of water receives excess nutrients such as nitrogen and phosphorus. This results in a plant and algal bloom that in turn rapidly diminishes the available oxygen and inhibits other life. Biomagnification occurs when chemicals or metals build up in a food chain. As the chemical moves up the trophic levels, it becomes more concentrated in the animal tissues and leads to health problems or death in predatory animals.
Industrialization and the use of fossil fuels have also changed our atmosphere, resulting in a changing climate. These changes in temperature and weather patterns affect how organisms can survive. While some organisms are able to move or adapt, many are facing changes that are too rapid for them to react to. This is leading to extirpations and extinctions across the globe. In these circumstances, organisms can become less resilient to other threats such as pollution, invasive species, and natural disasters.
Natural Events
Geological and meteorological events can also lead to habitat change and a change in the distribution of ecosystems. Volcanic eruptions and earthquakes can rapidly change a landscape. These changes may destroy the existing habitat but also may create new ones that provide new niches for different species to occupy. Hurricanes, droughts, fires, and floods can also have major impacts on ecosystems. Some ecosystems have evolved to weather these events and can recover quickly, but extreme alterations in an ecosystem's composition or habitat can eliminate support for entire biological communities. Over time, these forces can drive shifts in species composition and distribution.
