HIGH FLYERS THINK TANK

Extreme Natural Hazards

University of Melbourne, Tuesday 30 October 2007

Professor Nigel Stork
University of Melbourne

Nigel Stork has a degree in zoology and a PhD on ‘how insects hold on to plants’, both from the University of Manchester. After seventeen years in the Natural History Museum in London, he moved to Australia to lead the Rainforest Cooperative Research Centre from 1995 to 2006. He is currently the Head of the School of Resource Management at the University of Melbourne and Head of the Burnley Campus. His interests in global biodiversity issues have taken him to many parts of the world including many tropical countries. He has worked with several United Nations agencies including the United Nations Environment Programme and the United Nations Educational, Scientific and Cultural Organization.

Species extinction

One of the points I want to get across today is that we need people in many different disciplines to work together. For the last 12 years I have been running a Cooperative Research Centre and we have found that the greatest advances are made when people from different disciplines work together – social scientists and economists working with biologists and policy-makers.

Also, we tend to get caught in our own little silos. For example, my colleagues and I worked on tropical forests and another group of people worked on coral reefs, but we didn't talk to each other for a very long time. It is only in the last few years that we have improved the situation by talking to each other and working together.

Extinction, as they say, is forever. But my own view is that there has probably been rather too much attention on global extinction of species, which is probably much rarer than we think, and perhaps we ought to concentrate more on what happens with local extinction, because often the species that become extinct locally may play a very large part in the local species assemblages. Such changes can affect key processes, and that may result in massive changes in the ecosystems. Of course, simultaneous local extinctions mean that you actually get global extinction of a species.

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This is a quote from Norman Myers, a great visionary.

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Time magazine had a nice article on some of the primates and how they were being preserved around the world. Where did the '100 species a day' come from? I still have not found a credible source. Yet it was quoted recently in the UN report that has just come out. As scientists we really should look at some of these statements and critically analyse them. As far as I can see, there still is no evidence of those kinds of extinction rates.

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Many of us would be familiar with the five so-called mass extinction events, but extinction is a natural occurrence, and the background extinction rate over geological time is probably about one species per year.

So where, geographically, have these extinctions taken place?

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This is from a global biodiversity assessment report of about 10 years ago, and is for birds and mammals. You will see that the total number of extinctions is really rather low. A few hundred species of birds and mammals are known to have gone extinct in the last couple of hundred years, and they were virtually all from islands. This is the current data we are still working with, so currently extinction really has been a phenomenon of islands for these terrestrial vertebrates.

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What we have also seen in the last 30 years is that the sorts of emphases on what the threats are that actually result in extinction have changed over time. I am just going to focus particularly on one of them, habitat loss, and particularly the loss of tropical forests.

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Scientists became alarmed when Norman Myers, again, reported 20 or 30 years ago about the major loss of tropical forests around the world. The central column of this slide shows some of the predicted extinction rates, using the reverse of the species-area curve following Myers warning. Basically, it is saying that if we are losing all this area of forest, then we must be losing all these species. People were predicting 20 to 30 per cent of global species loss per decade. So by now we should have lost 60 per cent of all species, if they were right.

As scientists we have to critically analyse some of the premises on which these statements are made. Very eminent people – Paul Ehrlich, Peter Raven (President of the Academy of Science in the US) – were making these kinds of statements.

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In fact, when you look at tropical forest loss, you see that most of the tropical forest loss, say in South America, has been of the dry tropical forests. And probably 90 per cent of the moist rainforests of the Amazon is still intact. But things are changing, and they are changing very rapidly. Literally in the next 10 years we could see massive changes there.

Bill Laurance from the Smithsonian Tropical Research Institute and his colleagues did an analysis. They recognised that there was about US$40 billion of development money from the Brazilian government on the table for new infrastructure in the Amazon region. They asked what the consequences would be for the Amazon forest if this entire infrastructure was created, roads and so on creating new access. In this slide the black areas are where it is really heavily deforested or degraded; the red areas, moderately; and the green are the pristine areas. Their pessimistic estimation was that possibly only 40 per cent of the Amazonian rainforest would stay intact.

One of the most worrying recent advances is the development of varieties of soya bean which will grow in moist, humid conditions, and we are now seeing large areas of rainforest being cut down to grow soya bean in the Amazon. Elsewhere, in places such as Borneo, people are cutting down rainforest for palm oil. Why is there such an increase in the production of these products? The new biofuels industry. These new developments are likely to dramatically affect our tropical environment.

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Discussions about extinction, particularly in Nature and Science, have taken very narrow approaches to the whole problem. Some recent papers by Joe Wright and Helen Muller-Landau from the Smithsonian Tropical Research Institute examined the trend of movement from rural to urban parts of the tropics, and suggested that the reduction of populations in rural regions might lead to reduced extinction pressures in these parts of the world. But they may be misunderstanding how communities are operating in rural and urban regions. Studies in Brazil, for example, show that people may be moving to urban regions but they also retain their farms in the rural regions, and they go backwards and forwards – just as people do here in Australia.

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So why did these birds and mammals become extinct? We see a wide range of reasons. Habitat destruction was very important, hunting was important, as were invasive introduced species, international trade, wetland drainage – loss of wetlands – pollution, and so on.

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Let's take one area, Asia, where Richard Corlett, from the University of Hong Kong, has looked quite closely at this. Richard has shown that in the last two or three million years, with the rise of Homo species, the megafauna of the region – the traditional megafauna that you might have in a rainforest area – has diminished, so that only about 2 per cent of this area now has that megafauna.

And it also means that there are massive changes, as I said before, in the way that those forests are operating and the processes that are going on there.

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A great deal of the argument on extinction rates has focused on the charismatic bird and mammal fauna, and I truly believe that they are as threatened as people say they are. But when you look at these data summaries from May, Lawton and Stork, showing the estimates of lifespan from origin to extinction for a range of different groups of organisms, you see that the mammals actually have a shorter lifespan (in terms of millions of years) than the smaller organisms. My view is that the smaller organisms probably are much less prone to extinction than the larger ones. Hence I don't believe the big figures about extinctions.

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The threats to beetles and butterflies are very different. In summary, you can't use butterflies as the token indicator group for all insects, because they are not typical insects.

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Another part of the argument has been about whether things are going extinct because they are so closely linked to other organisms. This slide shows an example I gave a few years ago: when the last passenger pigeon went extinct, so did two species of lice. In fact, that was actually wrong – but it doesn't really matter; the argument is still the same! One of the species of lice was a misidentification, and the second one is actually found to live on other species as well.

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This group of scientists did a very nice job working out just how many species may go co-extinct with other species that they are closely linked to.

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Norman Myers came up with the idea that if we conserved a few of the 'hotspot' areas of biodiversity around the world, then we would actually preserve a lot of the rare and endemic species. The hotspots that are identified cover about 2.3 per cent of the Earth's surface, and they contain about half of the species of endemic plants and almost half of the endemic vertebrates. It seems a great idea.

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This is the distribution of those biodiversity hotspots. Conservation International has got massive amounts of funding now because of this kind of approach.

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But then another research group (Orme et al., Nature, 2005) looked at this more carefully. They looked to see whether the species richness for those birds and the endemism and threats for those things actually coincided. And they found that in only 2.5 per cent of the hotspot areas did those three factors coincide. So, just because they are narrow, small areas, it doesn't necessarily mean they are threatened or have the highest species richness.

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Climate change is very much in vogue now, in terms of understanding species extinction. I truly believe it is going to cause a major problem for us, and I am just going to look at that a little here, using some slides from the work of Dave Hilbert, from CSIRO, and Steve Williams, James Cook University as members of the Rainforest CRC a few years ago.

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What Dave did was to use an artificial neural network to model the vegetation that is in the upland forests in the wet tropics of Australia and then look to see how increases in temperature may shift where that climate envelope is for those cool upland rainforests.

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You can see that as it gets warmer...

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...this area shrinks.

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So 3.5 degrees was the sort of medium that people were talking about. It is virtually all gone, just a few mountain tops.

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Steve Williams has been collecting data on the distribution of the vertebrates in the wet tropics for the last 10 to 15 years. He found that there are about 800 species of vertebrates in the wet tropics. 10 per cent of those are endemic, and they are virtually all trapped in that upland rainforest. Those are the things that are cool-adapted, and they probably had much wider distributions when the rainforests were cooler and extended further in area. Here is one of his examples of a quite widespread species in the uplands, the tablelands of North Queensland, the grey-headed robin. This is the present distribution.

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This is with 1 degree warming. It has gone down to about 86 per cent. And with 3.5 degrees warming it has gone down to 7 per cent of its range.

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So do these species have resilience? Are they able to genetically modify? People may ask, surely we are going to get some evolution with climate change? Ary Hoffmann, a Federation Fellow at the University of Melbourne, has looked at some of this with fruit flies. He has looked at one particular species of endemic fruit fly that lives up and down the rainforest patches shown here. So it is quite widely distributed.

He showed that that endemic species, when subjected to a clinal variation in the amount of water availability, showed little ability to evolve after 30 generations. By comparison, Drosophila melanogaster, the common fruit fly everybody uses in their experiments, could adapt very easily to this.

That is an indication that these widespread species, the invasive species, will adapt to climate change and therefore we are going to have more problems with invasive species than we have seen before.

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To go back to Steve Williams' vertebrates, up in the wet tropics: what do we do? Do we just let those things disappear? Should we try to conserve them in zoos, and try to keep captive breeding programs going for the next 150 years – possibly until it gets a bit cooler? Or do we try to move some of these things and see whether they can go to, say, Lamington National Park, further south? These are big ethical questions that we haven't really tackled yet.

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What we are seeing is that a lot of these factors are all interacting. I am not going to talk about hunting or harvesting, but we are seeing a lot of these things interacting. The example I am going to give you now is to do with the Great Barrier Reef.

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I am not going to talk about coral bleaching or anything like that; I am just going to talk about some really rather insidious things that are affecting the Great Barrier Reef and I am indebted to Professor Richard Pearson of James Cook University for most of the following slides.

As you can see, it covers about 2000 kilometres. It is an extraordinary icon for Australia.

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If we look at land clearing between 1990 and 1995, we see massive land clearing in Queensland, particularly in the areas which border the Great Barrier Reef but also down south in Victoria and in southern Western Australia as well. These data are from the Commonwealth State of the Environment reporting.

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Not surprisingly, we have terrible problems of water turbidity because of that land clearing, and cattle overgrazing up in North Queensland, particularly in some of the drier areas.

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This graph shows the rise in the increase of total area of sugar cane in the last 100 years in Queensland, and associated with that is the increased use of fertilisers – the massive use of fertilisers.

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Water quality is a major issue in the agricultural areas of Australia.

I should say that this is typical of what is going on around the world. After the Second World War there was huge concern as to whether there would be enough food to feed the world's population, and a lot of effort went into creating new varieties of plants and crops. I have to say that it was extremely successful. The availability of food has increased massively in the last 50 years (as has the price of food). This increase has been at the expense of the environment and the species that naturally occur in it.

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We impound about 25 per cent of our water – it may even be higher than that – and thereby change the regulation of the flows.

The solid line on the slide is the natural plot of the flow of rivers between the wet season and the dry season, and by impounding water in dams we change the environmental flows. And most of our rivers have been affected in this way.

That changes then the biology of the organisms, and whether they can survive or not.

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Another incredible problem is the loss of wetlands. We drain so much of our wetlands. This table from Professor Pearson and his colleagues refers to different forest types in different places – Mulgrave-Russell in North Queensland, the Johnstone catchments and so on. Just note that every one of these has a negative figure: probably 65 to 70 per cent loss of wetlands, of all these different kinds of different wetlands.

The wetlands are where an awful lot of amelioration of the pollution and the sediment load takes place, so we are just shoving this stuff straight out to sea rather than having it go into those wetland areas.

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The result is not surprising. The slide shows a simulation of some of the flood events on the Burdekin River, showing the way that the nutrients and the sediments are going out to the Great Barrier Reef.

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I thought I would show this graph to try to get across to you the population problem we have. These are the people that need to be fed around the world – I suspect some of you will be surprised at the size of some of those populations.

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But this is what is going to happen with global temperatures by 2050, we are told. It is going to get hotter virtually everywhere, particularly at the Poles, but in many other areas as well.

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Similarly, the rainfall patterns are going to change in various ways.

So one of the things I want you to think about is that we have got massive populations in some places and the breadbaskets of those areas, the places that produce all the food, could change quite dramatically. We could have billions of people who are starving, not just the odd million or two as we have seen – instead of 10 million in Africa we could see billions of people.

What I am concerned about is that we knew about climate change in the early 1990s. When the Convention on Biological Diversity was signed, we had extensive information on climate change and there was a summary agreement between the scientists on climate change. Governments have known this for 15 years. But the problem is that it has been portrayed as a 'green' issue, and the climate scientists, I believe, didn't get the social scientists and economists involved early enough to get across what the social impact has been.

So that is an area that we have really got to think about. We can't just work on our own as geophysicists or biologists; to make some major changes we are going to have to work across disciplines.

Finally, will Homo sapiens become extinct? Well, of course it won't, because it is an invasive species with a great ability to adapt to its environment and to adapt its environment.