h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I am somewhat concerned about the current trend in environmental reporting in the newspapers and other media. Most of it revolves around global warming. Now that's actually good and necessary ... our society must absolutely figure out what the effects of global warming will be, and if we could do something about it. But there's another crisis equally important: the decimation of global biodiversity.

(Nerd note: 'decimate' initially meant 'to reduce by a tenth' and long ago it was used as a military method for penalising soldiers who underperformed in battle: after battle, one tenth of them would be executed. Currently the word 'decimate' often seems to imply a greater reduction than by a tenth ... but in the case of biodiversity, even a reduction by a tenth would be substantial harm... same as executing every tenth soldier in a legion; you're just reducing your military strength ... and you're totally destroying any kind of sense of comradeship and loyalty in your troops ... which is why 'decimation' is no longer practiced in the modern military.)

OK we're speaking of the world-wide destruction of biodiversity. This destruction results from various causes: global warming might soon become the most important cause so yes, it ties in to the current mainstream media debate, but there are other causes as well, primarily, the destruction or alteration of habitats by humans.

Destroying a habitat can be done directly: for instance, a patch of rainforest can be clear-felled so that only a bare open patch of ground is left. All the plants are removed, and with them, go all the animals that depend on them as well.

Sometimes 'habitat' is not destroyed as visibly as this, but subtly altered ... but all the same, altered to the point where its original inhabitants can no longer live there in the same numbers and in the same balance as before. Some such alterations are caused directly by humans, other times they are secondary effects of human activities.

Then sometimes, though habitat is largely left as it is, creatures in it are selectively removed or harmed by humans or human-related factors, causing an impoverishment of the biodiversity of the area.

But I don't want to talk about all the ways in which humans destroy biodiversity - I want to talk about biodiversity itself. Because, we need to understand the *value* of this diversity, if we are to know how important it is to do something against its destruction. We need to understand what sort of a priority we are to make of it, in our environmental efforts. Many environmentalists are very committed to what they do, but still lack an understanding of the various dimensions of biodiversity, and this makes for less-than-optimally-efficient conservation policy.

So ... what is biodiversity? The word 'diversity' means 'variety', many different kinds ... and 'bio' signifies life and living things. So biodiversity means the total variety found in the living things on this planet: different shapes, sizes, builds, lifestyles.

There are important things to know about the biodiversity we have right now. The first is, how it has come to this. All living things are most probably the descendants of very simple single-celled living beings that arose on this planet probably between three and four billion years ago. Those first living things were very simple and similar to each other, compared to the bewildering complexity of things that live today. Over time, the first living things have changed - evolved - and became more complex and also became different from each other. Different groups of things evolved from those first ancestors. Ultimately, all living things are descended from those ancestors ... and all are in a way related by blood, by direct descent from shared ancestors. We are in a way 'kin' not just to apes, but to mice, to birds, to lizards, to fish, to insects, to trees, to bacteria, and everything else. The relationship is there ... it's just a matter of distance.

So: the biodiversity of today is an outcome of evolution, of change in living things over thousands or even millions of generations.

The next thing to know about biodiversity is that the biodiversity we have at the moment represents only a tiny fraction of the biodiversity that has existed on this planet since its origin. Living things change and evolve. Many kinds of living things *stop* evolving at a point, though. Even though complex things like mammals and birds have evolved, there are still very simple things very similar to the single-celled ancestors of everything. So ... new forms arise, without the old forms necessarily being discarded. But sometimes certain forms go extinct: at some point, they just disappear. Extinction usually happens when a species cannot replace individuals that die, by new individuals being born. This can happen for myriads of reasons. Sometimes it is due to environmental catastrophes. Sometimes the causes are more subtle. Whatever the case ... extinction selectively cuts twigs and branches from the 'tree of life'.

I want to adress one particular misconception: that the species that go extinct, are somehow 'unfit'. The idea of the 'survival of the fittest' is something that has unfortunately found its way into the minds of the public as well as many scientists. In reality if we examine extinctions, we see that pretty much every species or larger group that went extinct, actually was 'fit' for a certain time and place or way of life, but was unable to adapt to changing conditions ... its 'niche' in the world became too small for it, or something else squeezed it out of it. If the niche had remained, the species would have remained too, and might even have given rise to new species adapted to new niches.

Over the course of evolution, incredible numbers of species have gone extinct, at various periods. Often, extinctions have occurred together, and often they've been global in scale. Some crisis hit the entire planet, and made life impossible for a huge variety of different things. These 'mass extinctions' have periodically decimated life on the planet long before the arrival of humans. In each case, the diversity of life was significantly diminished, and millions of subsequent years of evolution was necessary to supply new species in the place of those that had vanished.

That is the good news: evolution goes on, and as long as *some* living things survive, evolution will create new living things from them again.

The bad news is that it takes very long. After the extinction of the dinosaurs, for instance, it took about ten million years of evolution before the food-webs were again as complex and stable as they were just before the extinction.

Like I said: the biodiversity we have now, represents only a tiny fraction of the full diversity of species that have ever lived on Earth. There probably have lived a thousand times as many species as there live at the moment.

But apart from all the things that *have* lived, there's the biodiversity of a specific moment to be considered: 'freezing' the planet in time and counting the number of species on it, at that moment. If we could do this with our planet right now, we probably would find several millions of species on it, most of them being insects. We are trying to do that ... we are trying to count all the species ... a monumental task.

If we could minutely examine the history of the Earth like that (which we cant ... we can only see crude evidence of past life in the form of fossils, accidentally made and accidentally discovered) ... we would see a pattern of gradually increasing biodiversity, over time. The global extinction events were like 'dips' in the graph of ascending diversity ... but after each 'dip' the graph went up again. Evolution continues and more and more diversity of forms and ways of life develop. Every extinction ... while removing some forms ... make way for the development of new forms. Again, that's good news.

But all is not good news. It is nice to know that evolution will produce new diversity ... but there's the problem that *right now* we seem to be in another global extinction crisis ... this time one caused by our own activities. And we may see in our own lifetime ... or that of our children or grandchildren ... a reduction of diversity that is so bad that it disrupts the global ecology ... it causes the collapse of food webs, and such impairment of biological productivity that the planet can no longer provide food or the other means of sustenance for us all ... us humans, and also our animal and plant relatives.

What is the value of biodiversity? I personally see this variety of life in 'spiritual' terms: it is glorious and beautiful, it enhances the value of 'living' ... wonderful and weird things, wonderful and weird ways of life, it is the exploration and fulfillment of the 'potential of Life' of which we and all other creatures are part. Biodiversity is a goal in itself. It is interesting. The Universe strives towards becoming more complex, towards higher and higher levels of ordering. We and all other living things are manifestations of that. Truly to me this is a very deep and important spiritual value.

But apart from the above ... which not everybody will 'see' or experience like I do ... there are practical values to biodiversity.

Let's look at a single creature. If it has diverse genes, diverse adaptive abilities and diverse behaviours in itself, it is more capable of coping with adverse conditions ... it is more capable of making it through changes. This in a sense is 'fitness' as Darwin meant it, though creatures that are 'less fit' may prove surprisingly resilient ... it depends on many things, but still: genetic diversity, adaptability and behavioral variety adds up to vigour and resilience of life.

Now lets look at an entire species. There is such a thing as 'diversity in a species'. That is when different individuals in the species differ from each other. Humanity is a *great* example: consider the vast difference between different individual human beings, even in what is considered to be a single 'race'! Indeed the differences between different individuals of a 'race' is often much greater than the 'average' difference between different races (which is why 'racism' makes little sense). Not only humans have these differences inside species ... there are huge differences in our domestic species as well, like cats and dogs ... think of the differences between the different 'breeds'! This diversity is to a large extent human-created ... and maybe with genetic engineering humans will soon create diversity much greater than this.

But the problem with human-created diversity is that the things we 'create' are not adapted towards functioning in self-sustaining ecosystems. Many of our breeds of dogs, cats, cattle and so forth, will never make it if the artificial circumstances we made them in and for, disappear. (A topic I hope to write about in depth later).

So let's look at species in Nature: our dogs come from wolves, and the many breeds of dog we have today, indicate that within the wild wolves from which they descended, there already existed an incredible potential for variation. This is not something we created ... we only worked 'with' it in selecting various different individuals from which we made the various breeds of dogs. But wild wolves, in themselves, in their genes, already had all of this variation. In Nature, wolves will not vary quite so much as domestic dog breeds do, because of environmental constraints, weeding out certain 'impractical' sizes, shapes and habits. But still, wolves differ a lot in things like size, coat length and colour, temperament, and more ... which makes the species adaptable and robust.

Many other species of plant and animal also contain within them, great variation between individuals. Variation is built upon genetic differences, but not only ... there is also the 'expression' of genes (a complicated subject). It may happen that some populations contain a much greater variety of genes than 'show' on the outside: they may look alike but their genes may be very different among themselves. Many populations may carry huge amounts of 'unexpressed' genes that may form the 'basis' of future variety ... when external circumstances change, the genes may suddenly start being expressed.

So: for any *species* it helps, enormously, to have different individuals with different genes, different abilities. This makes the species less likely to go extinct ... when circumstances change, there is a much greater likelihood that there will be members of the species able to adapt to them.

Species that are numerous and widespread, usually have a bigger 'library' of genes and behaviour than species that only occur in small areas, and that are rare. But this is not always necessarily so. There might be species that are limited in number and confined to isolated regions, that nevertheless have great diversity among themselves. But generally, it is the case that larger numbers of individuals in a species, have the *potential* for much more variation among themselves.

And it *certainly* is a factor that when the numbers of individuals in any species are greatly reduced, for whatever reason, a lot of genetic and behavioural diversity in that species will be lost. This is perhaps one of the greatest kinds of harm humans have caused ... the destruction of diversity *in* species because of the species having been greatly reduced in numbers due to human activity. So ... even though animals like elephants and gorillas still survive as species, there are much less of them than there were before ... and probably a much reduced genetic diversity. This leaves them more vulnerable to the effects of further changes.

From diversity *in* species, let's go to diversity *between* species, and especially, in the context of ecological webs. In Nature, ultimately, *nothing* exists in isolation. Though we conceive of food webs as being limited to certain areas, in truth they are dependent on other food webs, so we can speak of a global web of interrelationships and interdependences. But consider a small fairly well-marked ecological web ... a small island. There are plants on the island, and there are animals. Some animals eat plants, other animals eat other animals ... some eat both.

Now, many islands are vulnerable: sometimes an island is volcanic and, periodically, volcanoes will erupt. Sometimes an island is hit by a hurricane. Sometimes a disease epidemic breaks out amongst some of its inhabitants. Many such disasters may happen.

Now, an island with only one kind of plant, and one kind of animal eating that plant, is a rather non-diverse place. A disease epidemic may destroy all the plants, or all the animals, at once. But suppose there are ten species of plants on it, and thirty species of animals. A disease epidemic may remove one or two species of plants or animals but the others will be unaffected because of being *different* from the one targeted by the disease. Another kind of disaster may wipe out a few species, but again, others (for various reasons) will survive.

But this island, when hit hard, will take long to recover. Perhaps a hurricane might wipe out fully half of the plant species ... the extinction of which might take two thirds of the animals species out as well. It will take a long period of evolution to restore the erstwhile diversity.

Now imagine an island with a *hundred* species of plants and a *thousand* species of animals. This island will be much more robust than the one that had only ten plant species and thirty animal species. Even a huge disaster will not easily wipe out half of all the species. And after the disaster, there will likely be survivors that can virtually *immediately* change their ways of life and move into the gaps left by those that have vanished.

Another factor is productivity, and the means to sustain life. A new island, at first (say after having emerged from the sea due to volcanic activity) is barren and the soil is infertile. As plants establish themselves, they actually improve the quality of the soil. As they diversify into different species, they start making new habitats. Some plants grow better in full sun, others grow better in the shade of other plants or rock overhangs. The plant roots break up the stony ground into fertile soil more easily penetrable by roots of yet more plants. Plants drop leaves which become part of a layer of leaf mold and humus, rich in nutrients in which new plants can grow. As the island becomes clothed in green, the sunlight and rainfall landing on it gets used by more and more plants ... and the more plants there are, and the more different *kinds* of plants there are, the greater use will be made of the sunlight, the rainfall, and the nutrients in the soil.

And animals will come too. The animals will make use of the plants. The more plants, the more animals that can live on them; and the more *kinds* of plants, the more *kinds* of animals that can live on them. Plant life gets turned into animal life ... the 'plant resources' are now used as well; the greater the variety of animals, the more efficient the use of the 'plant resources' as well.

All this translates into bioproductivity: the 'production' of living things in a rich and wonderful variety, from the 'non-living stuff' of the environment.

Now just like an island, so too the planet. Just like *any* ecosystem is more robust and resilient, the more species it contains, to too the whole planet is more robust and resilient, the more species it contains ... and the greater the variety of forms and lifestyles in those species... and also the more complex and diverse the 'genetic libraries' of those species are. Just like an island, the greater the diversity of living things - plants and animals - the better and more efficient 'use' that is made of its resources. Biodiversity boosts bioproductivity.

So there are practical reasons as well why more biodiversity is better than less.

I'll go into some of these issues in greater depth in following postings ...