As Habitat Shrinks, Extinction Grows
As we deforest and build over habitats, we are shrinking habitats and disconnecting animals from each other. The effects of this is being felt by mammals, whose extinction risk grows as habitat fragmentation increases.
Habitat loss is the number one threat to our fellow species. With nowhere to live, animals have nowhere to go, and they die. Simple as that.
Therefore, it's pretty obvious to say that when animals are left without habitat, or large enough intact areas of it, they are at greater risk of extinction. Fragmentation of habitat happens when chucks of habitat is destroyed and this pushes animals into smaller and smaller areas of habitat. This restricts their food, their ability to find a mate and therefore gene flow, and leaves them more vulnerable to threats.
With smaller areas of habitat rather than one big, continuous area of habitat, there are more “edges”, that is, boundaries between one habitat and another. This creates “edge effects” which are changes in the population or community structure that occur at these edges. Under natural circumstances, edges can exhibit great biodiversity within these boundaries, however under human influence, edge effects can be hugely detrimental to species.
Some examples of this will give you a better idea of the concept. Edges allow for invasive species to creep into the inner areas of habitat they they normally would not have been able to reach. Fires are more likely at the edges and fewer areas are protected from them, similarly these areas are less protected from pollution. Roads ploughing through habitats not only destroys those areas and puts animals at great danger from vehicles, they allow for greater access by humans. If these humans happen to be poachers, then it means that more animals will be accessible to kill for profit. At the edges, sunlight and wind are much more prevalent so environmental conditions change and so will the species who live there…and clearly climate change will have an impact.
The threat that habitat fragmentation poses to species is obvious, but it has been backed up by science. Research on mammals (4,018 land-dwelling species to be precise) shows that species with more fragmented habitats are at greater risk of extinction. Even when factors like geographic range and body size were taken into account, fragmentation of the places they live is a huge predictor of extinction - it threatens mammals big or small, wherever they live.
Hotspots of fragmentation include South America outside the Amazon rainforest, parts of south-central Asia, eastern North America and Europe. And I’m sure I don’t need to tell you what the main drivers of fragmentation are? Of course, it’s human activity, such as urban development and deforestation.
The research showed that protected areas aren’t really helping either. Very little key mammal habitat has been set aside for conservation - just 3.6% of the average species’ range consists of high quality habitat within protected areas. In fact, there aren’t enough protected areas in general, but that is for another blog post another day…
So worldwide, fragmentation is a pretty major threat. Its ironic that as we become more connected and the world becomes smaller as we travel it in our vast numbers, non-human animals are becoming increasingly disconnected. Landscapes that were previously connected are becoming broken up and confining animals into smaller areas. They will increasingly be unable to cope with risks within their habitats and certainly will not be able to move out of them if conditions become unsuitable for them, when climate change really, really begins to take hold, for example. It feels like, as we’re changing the planet more and more, we’re making it harder and harder for animals to adapt.