Predicting Biodiversity

This podcast originally appeared on Pythagoras Trousers episode 106 on January 17th 2013

Predicting biodiversity is an interview with Blake Suttle about how we can watch the movements of plants and animals to be able to predict their movement in the future.

Transcript:

Our little blue planet is going through a bit of a hard time at the moment. It’s been taking on the forces of climate change, and adapting with a brave face.

It is easy for humans to see how we are affected in our different societies. Increased rainfall floods towns, rising temperatures melt the icecaps, rising sea levels will cause entire countries such as Kiribati and Seychelles to vanish under water.

Plants and animals will also feel the pinch. Ecosystems will have to adapt to new weather systems, and some animals will have to move to new areas to find food, water and shelter.

According to the Intergovernmental Panel on climate change in its report released in 2007, climate change will alter the structure and function of most ecosystems, will reduce biodiversity, and will therefore compromise the ecosystem services required by all life on Earth.

Thousands of years of evolution, creating some of the worlds’ most beautiful creatures is being destroyed due to some of the affects of climate change. Scores of amphibians in the South American rainforests have become extinct as warmer, drier climates have increased the amount of diseases circulating in the areas.

Scientists have been trying to predict how climate change is going to affect our planet over the next 50 to 100 years. But all life on our planet is so interlinked, how will we know what is going to change? Will we be able to model all possible outcomes of climate change on computers, and then know what to prepare for in the future?

Dr Blake Suttle, from Imperial College London, has been studying the affects of climate change on biodiversity for near on 15 years now. He looks at how we can know what we can predict about how global warming will change our planet.

I would argue that that is important to how we manage the future climate change impacts, and that knowing what we can and cant know about the future is as important for managing climate change impact, as actually having these predictions of what biological changes will happen.

So that’s a long way of answering your question, but my work isn’t so concerned with particular plants, or particular animals, as with all plants and all animals. I’m not particularly interested in one ecosystem type, or in another. I’m interested in how we can know how any ecosystem will respond to climate change over the next ten, twenty, fifty years.

So the work that I do tends to be in systems with relatively fast generation times of all the organisms. So primarily I work with California grasslands, which are dominated by annual plants, by plants that complete their lifecycles in a single year. And that are dominated by annual insects; insects that complete their, each generation within a year. And that means that… Now I’ve been doing this experiment for about 13 years, where I actually manipulate the climate over these large communities, in terms of altering the seasonality and intensity of rainfall experienced by these grassland communities. And that manipulation has now been going for 12 years, and that means that I’ve been, that these communities have experienced climate change through 12 successive generations. And so what I’m looking to do over here is set up research around the Mediterranean basin where we can get similar systems with very fast dynamics, with annual dynamics.

You know, if I work in a grassland in the UK, where the grasses may live to be, a single grass organism may live to be 50 years, there are these long perenials, it would likely tell me the same answers, but it would take me very much longer to get those answers. If I do an experiment for 10 years over an annual community, then I have 10 generations of this dominant organism in this community responding to climate change. 8.44

Living systems are complicated; there are relationships between different species that are intricate, and highly dependant on many things. But when it comes to making predictions about how these relationships will change, couldn’t we look into the past? Could we go back far enough to a time when this type of change happened before, and study how Earth adapted?

A lot of the understanding about climate change, not just the biological side, but the physical side as well, comes from looking into the past. There were a number of scientists who, in the field of paleoecology, they tend to be less concerned about climate change because if you study the plystecine extinction, where 10k/11k years ago, where all of the mega fauna in the US went extinct within the span of a few hundred to a thousand years, then the types of predictions that we’re talking about now may seem less dire than what you’ve already studied through the record.

Now there’s a lot of research trying to piece together the extent to which the declines and losses of all those Pleistocene mega fauna were driven largely by climate, were driven largely by fire cycles (that may or may not have been linked to climate) or driven largely by the invasion of human beings, homo sapiens, into the continent, over the baring landscape.

What’s equally valuable is looking at the changes we’ve seen over the last 50 years. And what we need to know, part of the focus of my research is the extent to which we can look at whats happened over the last 50yrs and extrapolate that forward to the next 20 or the next 50 years. If we could just draw a linear relationship over all the climate change we’ve seen from 1960 to 2010, and extrapolate that forward to climate change we’re likely to see from 2010 to 2060, can we just biological impacts out along that same line? Can we maintain those same relationships? And there are some reasons to think that we can do that, and that tends to be where we often start. But there are a number of things that get complicated as we try to extrapolate that way. One is that the future that we’re moving towards, many systems, it’s referred to in science as non-analogue conditions. So we’re likely to encounter climate regimes that there is no precedent for in the modern times of observation. So combinations of seasonal temperature and precipitation regimes that there is no past analogue data for. Another is that biological systems don’t tend to behave linearly. So we may describe some phenomenon we’ve seen with a linear relationship, and try to extrapolate forward, um one thing that ecologists warn about and often see in our research is that because species interact, because no individual organism, or no individual population or organisms or species experiences climate change in a vacuum. Instead, any given species is experiencing climate change amidst all of the surrounding community members that are also experiencing climate change. So what we see are changes in interactions up and down the food web that can really drive predictions into disarray.

Ecosystems require a delicate balance of energy flowing from one source to the next. A specific variable, say increased temperatures, may alter an energy flow by reducing the production of energy, which could then have an affect on the receiver, and the next, and so on.

So the simplest example of this is maybe from my work in California. You have a given plant, and you know how temp and rainfall in different seasons affect that plants’ biomass: affect its production, affect its seed output. We may look forward, look at the climate future and say oh well those conditions you know, if its going to warmer in the spring, and there’s going to be more rainfall, well that should favour that plant. We know that warmer springs and wetter springs, favour this plant. So a straightforward prediction would be: there will be more of that plant, that plant will be better in the future. But, If you consider that a herbivore, or a consumer that feeds largely on that plant, or exclusively on that plant, is also favoured by those warmer springs and wetter springs. And then you might say, oh ok, so physically this plant should be favoured, but biologically, this plant should be disfavoured because the thing that eats this plant and only this plant is going to be that much better as well.

And its how we balance out that direct affect of climate on the plant with the indirect affect of climate on the consumers of the plant. And it gets less straightforward still when you consider that it’s never an issue of just one species and it’s consumer. There is how a species will be affected by the physical side of climate change, and how the pathogens and the diseases that that species gets can be affected. How the resources that species requires will be affected, how the competitors, the thing with which that species competes; how the consumers of that species, the parasites of that species. So things become non-linear very very quickly when you begin to try and incorporate all of these additional ecological interactions into species’ futures.

A challenge now is to begin to identify which ecological systems behave in a linear fashion, and which behave non-linearly. From this, it may be easier to get an idea of which species, and which systems as a whole lend themselves to predictability.

So for example, a food chain as part of my research in the early work was when I was just out of university in the Yellowstone national park, looking at interactions between wolves, which were reintroduced in the 1990’s into Yellowstone, and the elk and moose on which wolves feed, and then the scavengers: the things which feed on those elk and moose once they’ve been brought down by wolves, and once the wolves have had their feed. And the things that those elk and moose, the plants that those elk and moose feed on. In ecological park land, wolves tend to be very strong interacter. So the food chains that connect wolves to moose to fir trees on which the moose feed are very linear. And there can be a number of interactions, that each of the species may have other consumers, resources and competitors, but those three species have such a strong role in that interaction that we should be able to ignore most of those interactions with other community members, and look at how wolves are going to respond some level of warming, look at how moose are going to respond to some level of warming and look at how fir trees are going to respond to some level of warming, and make pretty strong predictions based on that understanding.

What we’re learning from ecology is that there are some systems that can be defined by food chains: by the idea of a preditor trophic level, a herbivore trophic level and a plant trophic level. And there are some systems that can only be classified using food webs. And that’s the classic picture of everything interacting with everything else, and everything going all over the place. So that is really the challenge that ecologist are confronting, both the experimental ecologists and theoretical ecologists (people who work with computer models) try to tease out: what sort of characteristics of species suggest that they are going to be, that they will behave more predictably, or more non-predictably.

The mix of science and policy is still a bit of a grey area at the moment. Scientists used to put discussions at the end of their research papers, urging policy makers to see the global importance of their work, that something needed to be done. We are all trying to do little bits; recycling our waste, cycling instead of driving, but collectively, as a species, it’s very difficult for everyone to combat climate change. Each country, even individual cities are affected in different ways, and reaching an agreement to adapt, or mitigate climate change is proving challenging.

Where biology is moving now in order to be helpful, ok so, the warning is, here is the  type of damage we are talking about, here is the type of change we are talking about and the negative consequences that will have for human societies, now its about maybe minimising. Rather than minimising the extent to which climate changes, because we are in a period of pronounced climate change, and for the forseeable future it seems like we’re going to remain in a period of pronounced climate change, so the physical world is chaging, the biological world is changing, biologists are now increasingly moving towards what we can do to minimise the damage caused by some amount of climate change.  So rather than ending every paper with a lesson on the extend to which climate changes, now we’re talking increasingly about reducing the amount of damage that that level of climate change causes. This is ties much more to where do we need to set up public health infrastructure to deal with dhengay fever in the future, to deal with elephantitis, to deal with malaria, these vector born diseases. Where do we need to think about establishing agricultural infrastructure, so that we can continue to feed the world, even as rainbelts and temperature regimes are shifting, and pests and pathogens of crops are able to expand their distributions into new areas. And in terms of the biodiversity conservation, where do we need to set up new protected areas, and how do we need to modify existing protected areas to maintain the levels of protection of biodiversity and the sort of sustainable flow of goods and services from ecosystems into human societie 50yrs into the future.

But it’s not all doom and gloom, like the new book Wild Hope by Professor Balmford describes, life is cropping up in new places, success stories always happen in the face of danger.

Not all of the impacts are negative, its not just, we’re talking about things happening on a pretty quick timescale, but climate change will create a lot of new opportunities as well. We’re going to be able to grow crops is new places. Its not just that existing cropland is going to disappear. There will be new cropland opening up.

There is also a balance between humans, animals and plants. We rely heavily on food produced on farms, whether it be cows, or grains. If climates change dramatically, so will the land and weather systems that govern these areas.

So my interest is in how biologists can take what we understand about that system and apply it to, eg someone in natural resource management, who wants to make sure that we have grassland that can provide forage to cattle and sheep. And where that is going to be. Where we should set up protected areas for wildlife conservation. Where we should set up agricultural infrastructure, looking into the future. And one thing that I think from the side of biological responses, what we can focus on is how a given species, at some natural reserve is going to change, or we can focus, sort of zoom out from individual species and say how is the diversity of these systems, how is the number of these species that can coexists together in this system is going to change. We can zoom out even further and look at how the function of that ecosystem is going to change: how will something like net primary production, which is pretty critical if you’re thinking about how many cattle you can graze, or how many elk a system can support. So we can look at the level of indicidual species, and we can ask how is the biomass of this plant species going to change, or we can zoom out and ask how will the number of coexisting species change, how will the biodiversity of the system change. We can zoom out even further and say how will the production change.

And what my work in California shows is that these big, aggregating variables like production and diversity behave much more predictably to a change in climate than any individual species. So when we try to narrow into a given site, to how an individual species will behave, well the performance of an individual species in a given place is tied to any number of complex factors. So it can be determined by so many different things that we’re really only good at understanding it AFTER we’ve observed the change.

 

 

For some systems, the driver behind the change will be rainfall, for others it will be rising temperatures. But all together, each little ecosystems depends on the others. Our little blue planet is a huge web of inter-linked lives, and the more we can do to help it in the future, the better.

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