diversity | Alloporus

Species go extinct because of the process that created them.

Ah ha, not the answer you were expecting. You thought I was going to say habitat loss, pollution, introduced pests, climate change or some other lefty topic sung about by old hippies and youngsters frightened for their future.

Indulge me for a few minutes and follow this little sequence of logic to the end of the post and you’ll see why extinction is more about the process of evolution than it is about humanity.

Polar bears and koala (not) bears

If you go to northern Manitoba, Canada, you can go out to the wilds and see a polar bear. There are even tour operators who will take you and look after you so the bears don’t rip your Gortex jacket.

You cannot see a wild polar bear in Australia.

However, if you go out to the Australian bush, into the right habitat types, keep your eyes keen, and have a bit of luck, you will see a koala. And, yes, a koala is not a bear, it is a marsupial mammal.

There are no wild koalas in Canada.

Canada, polar bears; Australia, koalas. This we know and take for granted. The reason is that all species have regions where they occur in the wild and regions where they do not go and have never been seen, except in a zoo. It’s called their geographic range.

Let’s extend this idea a little.

Bird species in Australia

There are 828 bird species in Australia that are known to be present. Some are rare, others common. Some occur everywhere and some are found in just one or two places or in the case of the King Island scrub tit, on one island. It would take a lifetime of twitching holidays to personally see all these species because it is also nature’s way that species have certain habitats and places they prefer.

Some species are super specialists and only occur in certain very specific habitats, for example, old growth forest. As there is not much of this habitat left, these species have a narrow range. You need to hike into the forest and be very patient in order to see one.

Other species are just about everywhere. The Indian myna or the house sparrow are familiar to half the people on the planet, even those who have never owned a pair of binoculars.

Even in a habitat that occurs everywhere, like open woodland or backyards, not all species occur everywhere. There will be a dozen or so species in the average Aussie backyard in Sydney only several of the species in the Melbourne suburbs will be different, and those in Brisbane different again.

This is normal and always has been. Some species are rare, some are common. Some are localised others are everywhere. Welcome to nature.

In fact, nearly half, 400 or so, of the 828 bird species in Australia occur nowhere else on earth. They are endemic or unique to the island continent or both.

Alright, I’ve laboured this enough.

The point is that this is what the process of evolution does, it creates diversity. Random mutation alongside natural selection results in diversity as organisms focus on the most efficient way to harness resources that they convert into more organisms.

If you prefer to replace organisms in the last sentence with genes, you get Richard Dawkins, Selfish Gene.

I use organisms because a gene does not do it on its own, it needs other genes to make a vehicle that can travel forward in intergenerational time. But, of course, Dawkins is right, really it is genes that are selected.

We are so familiar with the result of natural selection, namely a huge variety of species unevenly spread across regions and habitats, that we take it for granted. Don’t be stupid, everybody knows that there are no wild polar bears in Australia, it’s too hot for them.

Nature is made up of gene combinations that are the most efficient at converting the resources in a given place, given the conditions. This is what evolution does all the time, everywhere.

This is the bit you need to follow… given the conditions.

Specialisation happens as an inevitable result of natural selection. There are still generalists with a fine working model of existence, crocodiles for example, that have not changed much, but the majority of species become quite specialised.

The problem with specialisation is what to do when the conditions change. Just ask the dinosaurs how that went for them.

Again we accept that mass extinction 66 million years ago without blinking. A huge, diverse group of land animals all die out in a short space of time because a meteorite hit the earth and changed the conditions. They couldn’t cope with what the impact and its aftermath did to their food and shelter. It disrupted things too much for them to adapt fast enough. Except for the crocodiles who could switch to fish.

The 5th mass extinction that knocked out the dinosaurs and 76% of species alive at the time, is a dramatic, iconic example of change. Only, the thing is that conditions change all the time. And this means that species go extinct all the time. It is an inevitable part of the process.

I’ll just say this again. If conditions change (and they always do) and they change fast enough, big enough or for long enough, some species cannot survive and go extinct. Period.

This is just a consequence of natural selection creating diversity and the whirlwind of a spinning planet with a complex atmosphere, ocean currents and mobile continents generating change.

The flip side of change that causes extinction is the opportunity for diversity. Change things and gaps open up for new species to exploit. But we’ll save that idea for another time. Today we are on the extinction consequence.

Change and extinction are inevitable

Only this is not what you are told.

Take this example from the front page of the Guardian online feed on 31 March 2019 stating that record numbers of Australian mammals face ‘imminent extinction’ that includes this quote

“The report calls on the next Australian government to commit to a policy that no more of Australia’s unique wildlife species will be allowed to go extinct, and to ensure, backed by the necessary laws and resources, that this policy is fulfilled”
Wilderness Society’s national forest campaigner, Peter Roberston.

Pause and read that quote again.

This person is asking you to believe that extinction, a law of nature that has a history as long and deep as life itself, can be overturned by muppets in Canberra.

Come on, get over yourselves.

You are not that important. Human activity is the biggest current agent of change sure, but to think that a specific political decision can rewrite evolution means you really do not understand the challenge.

We could leave it there as today’s healthy thought. Only there is just…

One more thing

Thinking we can ‘save the koala’ forces us into a bind. We are now imagining that extinction is terrible, an awful result that must be prevented. So important is this premise we even ask the politicians to make a policy to stop it happening.

We would have a very different view of conservation if extinction were an acceptable option because that is what happens in nature.

The choice to save a species from extinction becomes a conscious one made with a clear understanding of cost and benefit. We may still want to save the koala or the panda or the Southern Corroboree frog but if we do it’s a positive choice.

Important postscript

This post simplified natural selection as just about honing a solution to shelter and food and secretly implied that competition for these resources is what sorts out the weaker options. This is true but it’s not the only way.

There is also sexual competition that drives specialisation. Just so you know, Charles Darwin figured this one out too.

Amazing.

Why the sixth mass extinction was inevitable

Palaeontologists have a fine time of it. They fossick around in obscure parts of the world where there are few people and take a hammer to rocks.

They have done this for generations, found lots of fossils, and come up with some interesting conclusions.

Here are five of them.

444 million years ago 86% of species were lost.
375 million years ago 75% of species were lost
251 million years ago 96% of species were lost
200 million years ago 80% of species were lost
66 million years ago 76% of species were lost.

These are, of course, the five mass extinction events in the fossil record. The last one being the most famous when all the dinosaurs copped it.

Here is another pattern they found

Over time diversity has increased despite these mass extinctions and several smaller ones in between them.

There are more species alive today than at any other time in evolutionary history, despite the obvious fact that humans are kicking the sixth mass extinction into existence.

This is the history of life on earth. It is dynamic with huge shifts in diversity but with an underlying driver powerful enough to increase diversity over time.

If you believe this evidence then a few core concepts become clear:

Extinction happens.
Large extinction events happen often enough to make another one inevitable.
After extinction events, diversity recovers
And for at least 150 million years the trend is for diversity to increase rapidly, noting that the non-avian dinosaurs were lost during this time.

Diversity happens because there is time enough for mutation and natural selection to hone any number of specialisms. When organisms specialise they are successful in a relatively narrow set of conditions. A proportion of species become vulnerable to change in those conditions.

Enter human beings. Modestly specialised initially but with a distinct advantage. They had the brains and communication to adapt to a wide range of conditions, especially when they tamed fire and then much later discovered fossil fuels.

Once in control of energy humans have appropriated over half the global biomass production, removed vegetation, getting rid of wildlife and altered the composition of the atmosphere. More than enough change for mass extinction.

Humans affected the change but change would have happened at some point. Tectonic plates moving to cut off ocean gyres, volcanic eruptions, another meteorite strike, it would happen soon enough, maybe 50 million years hence.

Is the reality of extinction too painful?

Perhaps it is. Perhaps we are just too much in the present day to accept timeframes beyond ourselves. Certainly, there will be huge consequences of extinction for our production systems, the ecosystem services we rely on, and the very liveability of the planet for our species.

We’ll need a lot of adaptation to survive.

What we might also remember as we plan for change and seek to retain what we can of the diversity of life, that extinction is real and inevitable. It is as much a part of the process of evolution as the creation of new types.