Habitat Fragmentation and its Effects on Natural Environments that Most People will Surely Ignore

You and your family are on a road trip, and, on the way to your destination, you all pass through a beautiful forest, a place that offers such a nice change of scenery after being on the road for so long. Seeing the magnificent trees, glimpses of the wildlife that reside there, and, escaping to the peaceful realm of the natural world, you hope that your time in the forest will last for a good while before exiting it. But, alas, this sanctuary comes to an end shortly after you entered it, so, the next thing you know, you’re all back on the highway with everyone else heading in the same direction. The only potential difference is that maybe you were the only person who took advantage of such beauty while the others didn’t pay much attention, something that more and more people don’t do nowadays. However, habitat fragmentation, such as in this scenario, is becoming far too common now for anyone’s good as it creates a living hell for the biodiversity that fall victim to it.

I had a similar experience the other day when I went to spend time by West Point Lake in my hometown of LaGrange, GA. I parked my car nearby one of the boating docks, ready to head into the woods and explore that fine evening with no distractions to worry about. However, as I entered one of the nature trails, I immediately saw that Chinese Privet was beginning to completely take over the surrounding environment, and, even worse, that the trail was going to end quickly. I had seen Privet before in areas by West Point Lake, but they were only in pockets, giving officials hope that there would be plenty of area to spare after working to remove them. The nature trail, on the other hand, was mostly covered by the invasive species.

Chinese Privet growing along the side of a tree

In an area that would take less than five minutes to walk through without stopping, I looked for the aesthetic qualities, finding Cherry Laurels, Magnolia, Sweet Gum, Loblolly, and other great trees that weren’t affected by the Privet. I examined dens under tree roots, noticing the patterns where the waters flooded and receded in the area, and I stumbled upon some finches scurrying for food after following their sounds. After removing as much litter as possible, I made it to the end of the trail after spending more than twenty minutes in there. Certainly, it’s key to look for the good in every environment, but, when you have more of a pathway than an actual trail that leads to a trashed picnic area, not to mention invasive species ravaging the environment, there are serious problems that need to be addressed.

When it comes to habitat fragmentation in general, biodiversity that are literally living on the edge of areas that have been fragmented are much more susceptible to harm. This includes negative effects caused by human activity, increased predation due to the exposed areas, increased disease and natural issues like inclement weather, and even an increased amount of invasive species. This phenomenon is known as the Edge Affect, impacting wildlife that happen to find themselves in the more dangerous part of the habitat while those that live deeper and past the ecotones have a greater chance of survival. This is exactly what areas like those around West Point Lake are struggling with.

A crane near a patch of land not too far from its position

Not only does habitat fragmentation result in the issues listed above, but it also lowers the carrying capacity of these areas, meaning that the maximum amount of biodiversity they can support before resources begin to run out decreases. Therefore, the survivorship of those that can be sustained in those environments significantly drops since more resources can be eliminated as a greater amount of the natural habitat is lost. If not managed properly, these patches of habitat can become prone to local extinctions. Not to mention, the wildlife in those fragments become confined to their surroundings and risk their lives if they travel outside them.

The altered landscape outside of the patches of fragmented habitat is known as the matrix, separating each patch of habitat available to wildlife. Bodies of water, roads, and other boundaries can be considered part of the matrix, and they all are proven to be harmful to species attempting to move from one patch of habitat to another. Think of all the animals that die in the road each year after trying to move from one place to another, mainly because of continued human development that destroys more of their habitat. Those unfortunate accidents are more prevalent as fragmented habitat patches become sinks when they were once sources.

A source is a patch of habitat where reproduction is greater than mortality, allowing populations to grow over time. These tend to be larger and more diverse patches where species can continue to exist for longer periods of time than those found in sinks. A sink, in contrast, is a patch where mortality is greater than reproduction, normally existing as smaller and less diverse patches that can’t replace individuals that have been lost fast enough. The conditions of them are exacerbated not only by human activity but also by stochastic events, including bad weather, droughts, disease, and other unpredictable occurrences that are not in anyone’s control.

Sadly, these events have a much greater affect on sinks that are smaller and isolated from other patches, thus making the threat of local extinctions even more terrifying. Indeed, small patches of land like the one I explored around West Point Lake are more at risk of falling victim to stochasticity, so taking action to protect and connect them to other patches, especially sources, will behoove every one of them. The positive changes of connecting struggling patches, or sinks, to sources reflect the Equilibrium Model of Island Biogeography first proposed by researchers MacArthur and Wilson. The model states that species richness is dynamic with new species arriving and older ones dying out, making the immigration and emigration of species imperative to the survival and longevity of a habitat.

A patch of land by the contiguous part of the lake

Just like how the model describes the fact that smaller islands have more extinction rates along with more isolated ones, the same goes for habitat fragments where the colonization rate is less than the extinction rates. In order to improve these habitats, the colonization rate must be increased while the extinction rate must decrease so that the patch will reach an equilibrium between the two processes. One of the best ways to aid patches, namely ones that are farther apart from each other, is to establish corridors between them so that species can travel from one to the other without hindering their survival. Even better, this kind of action can lead to what is called the Rescue Effect where species from one patch, usually a source, immigrate to a sink which rescues its populations before they can go extinct.

Conservationists today are working tirelessly to reduce the impacts that fragmented habitats face, but there is only so much money that’s allocated for their efforts, so, with that being the case, they have no choice but to choose which patches to purchase according to the amount of biodiversity that exists inside them. They have to be mindful of the cost of each hectare that makes up every patch along with the cost to establish corridors between patches with the goal of restoring sinks. Calculating the Shannon Diversity Indices as well as the Jaccard Similarity Indices between the patches provides quantitative data of the biodiversity that exist within them. From there, the researchers can decide which ones need the most assistance based on those values, keeping them from going over their budget. This can even help them with the decision as to which patches should be purchased based on how much more diverse they are from one another. The patches that have the greatest amount of biodiversity should be the ultimate aim before assisting sinks with the erection of corridors.

The concepts of the Model of Island Biogeography are similar to those of habitat fragmentation, making it an important reference tool to manage biodiversity in such fragments. Source: www.islandbiogeography.org

From their standpoint, we desperately need to recognize how valuable such endeavors are because too many habitats are either destroyed or are becoming too degraded to support the biodiversity within them. Speaking of degrading and fragmenting habitats, work has recently began near my neighborhood to develop a new subdivision, cutting and clearing out as many trees as possible to prepare for construction. The first time I saw the workers beginning to reduce the dense wooded area, one specifically filled with pine trees that help support a plethora of wildlife, I couldn’t help but feel angry since I have known and appreciated it for the whole time we have been living in our current neighborhood. What’s even sadder is that the city of LaGrange, Georgia persists in its efforts to further industrialize and create more urban areas, completely ignoring the habitats that are being threatened.

On a more prodigious scale, critical environments around the world are being ravaged for profit, shrinking them down to even smaller fragments over a long period of time until they are no longer sustainable for life. The Amazon rainforest has received some of the most alarming rates of deforestation as those who relentlessly cut down more trees most likely don’t realize that this special part of the planet provides up to 20% of oxygen alone for all human populations. There’s absolutely no excuse for natural habitats to be so heavily affected to the point where they depend on drastic measures to increase the flow of immigration from one to the other before local extinctions occur. But, when there is no other choice but to maintain such fragments, there are certain requirements that need to be met so that said management will be successful.

One of them is to make sure that all patches that are being conserved are not too far apart from one another in order to promote immigration and emigration. Of course, if they are naturally distant from each other, then the establishment of corridors linking them is a must so that those processes can take place without any interference. If there are a chain of fragmented patches, it would be ideal to establish corridors between all of them, similar to building bridges from one place to another so that commerce can be made possible, except that species will be identified as commerce in this analogy. For instance, let’s say that one patch contains at least one or two individuals of an endangered species while, right across from it, another patch contains ten or more individuals of the same species. To prevent the loss of those individuals, a corridor would serve as the solution, giving the two individuals on the first patch a way to immigrate to the second, strengthening the numbers of that particular population.

Another would be to have larger habitat reserves instead of small ones thanks to the concept of carrying capacity. Obviously, the larger patch will be able to hold and sustain more individuals than the smaller one, so, if you already are responsible for the management of the latter, making a corridor between it and its bigger counterpart will help stabilize colonization. To ensure that the biodiversity that live inside these patches will have a greater chance of surviving, including the resistance of external threats, there need to be little to no edges that make up their shapes. If you have a greater amount of edges around a patch, then more species that live near them will be harmed from predators, disease, invasive species, and an array of stochastic events as discussed previously.

Not Surprisingly, the shapes of the fragmented habitats matter just as much so that there will be enough room for species to navigate the areas. For example, if you have two patches, one being in the shape of a circle and another in the shape of a square, the former will, without a doubt, be the better choice. With a circle, you don’t have any edges to be concerned over whereas the square will decrease the amount of acres that species can travel without encountering one of the four edges. Shapes like rectangles and ovals will be too narrow for sufficient utilization, so patches that are circular will always be the kind a conservationist would want to manage.

To help solve the problems surrounding West Point Lake, despite being a potentially radical proposal, I would recommend shutting down all public access areas for a massive cleanup project so that fragments of habitat can be improved. That means removing as much litter and invasive species as possible, and, once those objectives have been met, more parts of the lake should be permanently closed and monitored to manage them more effectively. As for my city alone, there are way more areas that have been altered because of human activity, so there needs to be more consideration for the natural environment. When it comes to areas that the public can still have access to, there should be increased surveillance to stop littering or other acts that harm the habitat in addition to harsher punishments for violating those laws.

A Sweet Gum tree sapling from the nature trail

The only way that these environments can be maintained without hindering any more progress is to start being tougher on those who harm them, including the patches that need assistance the most. As a matter of fact, the picnic area at the end of the trail looked like a complete disaster due to the trash that covered almost every spot, the remnants of what were once illegal campfires, and the failure to keep it clean of invasive species. I understand that it’s almost impossible to completely eliminate all of the invasive species in an area, but I feel like there aren’t enough efforts to make the area safer for native wildlife. If it’s that difficult for the local officials to manage such small plots, I can’t imagine how much harder it will be for them to tend to the bigger ones.

This leads to, perhaps, the most important message from this article. Despite the efforts to maintain fragmented patches of habitat and to keep them sustainable for all wildlife, they still cannot beat the fact that contiguous habitats are much better. Contiguous areas are ones that are not divided into patches and are whole, like a mainland to an ocean. They are more secure than patches and offer better chances for species survival. Going back to the rainforest, it’s a contiguous habitat that is in danger of being completely destroyed, or at least the parts that haven’t become fragmented already. It’s such a vital contiguous habitat that it supports the greatest amount of species diversity found throughout our planet. Not only that, but all major biomes found at mid-latitude contain the most biodiversity due to the stable temperatures and weather patterns every year, including the Amazon.

In reality, we have no choice but to keep contiguous habitats healthy and sustainable if we wish to make a true difference for our planet. Then again, cases arise when there is no other option but to manage fragments, fragments that can be the borderline difference between the prosperity and the extinction of a species. Even in those predicaments, it’s crucial to keep human activity or involvement to a minimum, only intervening when it’s required and not for the pleasure of tourists. There is a difference between having fun at places like West Point Lake and just completely disregarding the well-being of the environment. A majority of those who visit the beautiful lake, a man-made one for that matter, are insulting the endeavors of conservationists whose goal was to create an environment to help our local wildlife, provide an environmentally friendly way to generate money into the city’s economy, and to provide a safe place for people to have fun, for we must strike a balance between ourselves and other living beings.

So the next time you happen to pass a little patch of forest, or any other patch of habitat, think of how much vulnerable it is because of its size, shape, distance to other patches or contiguous areas, and the amount of edges it may have. With that knowledge, take action and do whatever you can to make a true difference for the natural environment. We have seen too many times now where habitats have been wiped out for profit, so don’t let any areas you notice that are in such conditions disappear. Remember, what seems to be profitable now for humans as we gradually erase habitats will prove to be costly in the future, a heavy price that will be too much to pay back in full if our actions are left unchecked.

I’m a graduate from LaGrange College with a B.S. in Biology, striving to be a conservationist and to help our planet.

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