Have you ever gone on an extended holiday, only to come back and find your neighbourhood is not quite as you left it? It may have been something as small as some trimmed bushes, or perhaps some old neighbours moved out and some new neighbours moved in. In any case, something changed.
We might think of ecosystems as something constant – the Serengeti will always have lions, for example – but in reality, ecosystems are subject to change, just like everything else on this planet. Let's discuss the different changes to ecosystems, and the natural and human causes behind those changes.
Global changes in ecosystems
Ecosystems are communities of living organisms interacting with each other and their physical environment. Those interactions ensure that ecosystems are never static. Different animals and plants constantly compete against each other for access to resources like food and space.
This puts ecosystems in a perpetual state of fluctuation, ultimately leading to evolution by natural selection – that is, the process by which populations of living organisms change over time in order to better adapt to their environment. In other words, ecosystems globally are constantly changing!
Factors affecting ecosystems
Any ecosystem has two distinct factors or components. Abiotic components are non-living, including things like rocks, weather patterns, or bodies of water. Biotic components are living, including trees, mushrooms, and leopards. Living components must adapt to each other and the abiotic components in their environment; this is the fuel for change. Failure to do so spells extinction, meaning the species no longer exists.
But if ecosystems are already constantly changing, what do we mean by the term 'changes to ecosystems'? Well, we are mainly referring to events or processes that interrupt the way an ecosystem is already functioning. These are changes from without, not from within. In some cases, an outside event or activity may entirely destroy an ecosystem.
We can divide changes to ecosystems into two broad categories: natural causes and human causes. Together with evolution by natural selection, natural disasters and human-caused environmental degradation are the main ways any given ecosystem will experience change.
Natural causes of changes in ecosystems
If you've ever seen a fallen tree lying in the road the morning after a thunderstorm, you probably already have some idea of how natural events can cause changes in ecosystems.
But we're going a bit beyond small thunderstorms. A natural disaster is a weather-related event that causes widespread damage to an area. Natural disasters are not caused by humans (though, in some instances, human activity can make them more severe). Other natural causes like disease are not technically natural disasters but can cause similar levels of devastation.
Natural causes of changes in ecosystems include, but are not limited to:
Wildfire/forest fire
Flooding
Drought
Earthquake
Volcanic eruption
Tornado
Tsunami
Cyclone
Disease
Some of these natural events may occur in conjunction with one another.
Natural disasters can fundamentally change an ecosystem. Entire forests can be burned down by a wildfire or uprooted by an earthquake, leading to deforestation. An area can be completely flooded, drowning all of the plants. A disease like rabies can spread through an area, killing large numbers of animals.
Many natural disasters only cause temporary changes to ecosystems. Once the event has passed, the area slowly recovers: trees grow back, animals return, and the original ecosystem is largely restored.
The 1980 eruption of Mt. St. Helens in the United States effectively wiped out the ecosystem surrounding the volcano. By 2022, many trees in the area had regrown, allowing local species of animals to return.
Just as ecosystems change all the time, so does our Earth's climate. As the climate changes, it, in turn, causes changes in ecosystems. When the Earth becomes cooler, polar and tundra ecosystems expand, whereas when the Earth becomes warmer, tropical and desert ecosystems expand.
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