Habitat Destruction
Created | Updated Dec 30, 2011
The greatest threat to wildlife and biodiversity in our present time is habitat destruction. Now this might sound like a kind of impersonal process ... as if it just happens, like for instance tornadoes or floods or hurricanes, but actually, 'habitat destruction' is something that we do. It's not even something that happens as a result of what we do, like global warming ... which we can't even all agree happens, and if it does happen, it is unintentional, a side-effect. Habitat destruction is not like that. We do it, we do it actively, and we do it on purpose. And it's not a contentious issue: it is clear that we do it, nobody can deny it. And also unlike global warming, no-one is talking about it. And lastly: let me say it again, it is THE GREATEST THREAT to biodiversity – and consequently to the entire ecological integrity of Planet Earth.
What exactly is involved here? First of all: the Planet Earth has sustained life for the majority of its over-four-billion-year existence. Over the course of all this time, life has diversified into staggering numbers of species. Most have gone extinct, but still, when humans arrived on the scene, the planet had reached a very high point of diversification of the life that flourished on it. Even now we are not sure how many species there are, but the numbers are astonishing. There are thousands of species of mammals, reptiles, birds and amphibians, tens of thousands of species of fish, hundreds of thousands of species of plants, and the species of invertebrates must number in the millions – there might be more than ten million species of insects, for instance. We still haven't even counted them all, let alone tried to get to know them to any degree. Indeed, even where large creatures such as mammals are concerned, we are still discovering new species, and most of the ones we know about, we know pretty much nothing about apart from that they exist.
But all of this diversity has developed on this planet, and through ecological processes they have established a situation of what I'd like to call 'unstable balance'. It's like a tightrope walker: he is not stable but he manages to balance himself. So, there is a lot of competition between different species, and as a result some do go extinct as they are outcompeted by others, but the same process also allows new species to come into existence ... actually, more species originate than go extinct which is why over time biodiversity tends to increase. Also, this diversity is not equally distributed ... some groups are much more diverse than others, and some parts of the planet sustain far greater diversity than others.
So, for instance, tropical rainforests are the richest and most diverse habitats on land, while coral reefs are the richest and most diverse habitats in the oceans. Also, most species are local: restricted to certain patches of forests, or certain reef areas, rather than being widely distributed, such as occurring across entire continents or oceans.
Now humans come onto the scene. We invent hunting, agriculture and cities. And that is the start of the habitat destruction. Hunting is the least destructive, but even with removing large mammal species, the ecology of habitats started to change. Agriculture was worse. Where once grew fields of many different species of grass, with many other flowering species amidst them, we suddenly ploughed it all under to plant just one species of grass ... in some places wheat, in some places barley, in some places millet ... and so on, for various different agricultural communities. More land was wiped clean of native species to make way for human houses so that cities could grow.
That process started over 10 000 years ago and continues ... and it is continuing faster and faster. In today's paper it was reported that it is estimated that there are now over 7 billion people on Planet Earth. This number in itself tells you something is wrong because we outnumber every other species of large mammal (except ones artificially boosted by ourselves like cows, pigs, goats and sheep) by an almost absurd factor. Never in its history could the Earth support such numbers of a single species that is as big and demanding as ourselves. In fact we need ... or think we need ... a heck of a lot more than anything else, even things much bigger than ourselves like whales. And all the things we need, somehow have to be supplied by this planet.
So, habitat destruction continues. More land is cleared of whatever plants and animals used to live there, to make way for more farms and plantations, for houses, suburbs and cities, and for highways. Even our mining activities are destroying entire landscapes, and leading to pollution of our water sources. Not even the oceans are safe. We are changing the ecological structure of the seas by removing most large fish; pollution is leading to changes and extinctions, and coral reefs are damaged and destroyed as a result of our activities.
If global warming happens, that, on top of effects of pollution like acid rain and acidification of the oceans, could destroy vast swathes of natural habitat.
There are hardly any truly untouched areas left on Earth. Even the ones that look pristine from the outside, have already been affected in some way, their ecological balance becoming more precarious: the tightrope walker now on a slippery and fraying rope. Exactly what will happen, we cannot predict. But consider deforestation. In the past, very large areas on Earth were covered in continuous forests. As humans started cutting the forests, they have become dissected into mosaics of shrinking, separate patches. Many of these patches have become too small to sustain viable populations of the animals (and often also plants) that live in them. At some point entire forest communities could go extinct. Also, as the forest cover of the land is reduced, it could lead to permanent changes such as aridification (what used to be forest becoming dry grassland, or even desert).
We tend not to think of plants, but plants are the first casualties of habitat destruction. Just to give you a concrete example that I am witnessing with my own eyes. When our family came to Pietersburg, we were on the outskirts of town, and to the east of us was uninterrupted wild land stretching pretty much all the way to the Kruger National Park. That was about thirty years ago. In those three decades, which is less than the blink of an eye where the life of this planet is concerned, almost all of this wild land has been destroyed. Drive eastward now, and you will see vast areas covered with farms, plantations, towns and squatter camps, and mining developments. This means that incalculable numbers of wild plants have been destroyed. A single hectare of savannah can contain more than a hundred different species of grasses and other small plants, and ten to thirty species of trees. And my region has an absolutely fascinating diversity of plants. Not one of these is worthless so that we can say it might safely go extinct because nobody would care. Every single species is unique and studying it can tell us a lot about evolution, biodiversity and ecology ... even before we have started to analyse the different compounds it contains to see if some might be useful to us. But that, too, is very important. Plants are natural chemical laboratories, and contain thousands of compounds most of which we know nothing about.
But for me the chief value of plants is their beauty, their interestingness, and what they could tell us about how life evolves to fit different environments. For instance my own particular interest is succulents, and how they adapt to survive in arid regions. To get back to habitat destruction: here in my own suburb there are some very rare and very interesting succulents, one of which is (or perhaps used to be) a kind of daisy that has developed succulent leaves and stems, and an underground tuber. This species might now be extinct in the wild as a result of the expansion of the suburbs. Then there are other very rare species, such as an Euphorbia that also has tuberous roots and finger-like stems that grow into large cushion-like tufts. It, too, is totally unique, and restricted to a few low, rocky hills. The suburbs are now spreading closer and closer towards them ... there are already a few rich folks' mansions being built on those hills.
One could ask oneself how many unique species have already been lost. For instance the little succulent daisy was only discovered very recently ... a few years between discovery and extinction. It might have disappeared under the sprawling suburbs without anyone even having known it was ever there.
And of course, plants form the basis of ecosystems on land. Many plants have specific creatures that feed on them, whether those be big like antelopes and elephants, or small like caterpillars and slugs. And, especially, plants with interesting compounds in them (poisons most of the time – but these, too, can potentially be very useful to humans) are eaten by specialized insects. Then, many plants have specific pollinators as well. If they go, their pollinators follow. These insects in turn were food for other things. So, food webs are impoverished, and ultimately ecosystems are destabilized.
Even short of exterminating species, habitat destruction causes an erosion of diversity inside species. If for instance a species used to occur numbering in many thousands, and then so many are destroyed that you are left with mere hundreds, those survivors will likely no longer contain the full diversity of genes that used to be there when there were thousands. This is another thing people don't often realize. Species in nature are not uniform. All the individuals don't look the same and don't all have the same genes. This is how it should be. The more genetically diverse a species is, the more robust and adaptable it is. Destroy 95% of the individuals, and you're likely to be left with just a small sample of the genetic diversity that used to be there, and you're leaving the survivors in an impoverished and precarious condition. Imagine if for instance humans were wiped out with, say, only about two or three hundred people escaping the calamity ... how about we make it the population of the isolated, subantarctic island of Tristan da Cunha (currently numbering about 260 people). How much of the full cultural and genetic diversity of our species would those people represent? (For interest's sake: the residents of that island are mainly descendants of Brits, and speak a somewhat archaic-sounding English dialect. Also because of their low genetic diversity they have unusually high occurrences of some disease conditions, specifically asthma and glaucoma. Furthermore the population is also vulnerable to calamities like volcanic eruptions and cyclones. Now imagine how precarious our situation as a species would be if those were the only humans left in the world ...).
This very sort of thing is what happens now with practically every non-human species on Earth. Even the ones that are not extinct, are being reduced in numbers, more and more and more. So we are wasting more and more of the diversity of the planet.
We cannot ignore this. We are dependent on the ecology of the planet. It has to keep on working, and the best way to ensure that it keeps on working is to try and maintain it in something close to the working condition it was in before we arrived on the scene. The diversity of different living things is not only a key feature that helps keep local and global ecologies robust and stable–in itself it is also fascinating, and surely one of the wonders of the entire Universe. We ourselves are part of that wonder ... and by destroying that wonder, we are ultimately also harming ourselves. Wouldn't it be better to cherish and nurture it?
