[NOISE] [MUSIC] Which is true? A, methane is a more powerful greenhouse gas than carbon dioxide? B, carbon dioxide is a more powerful greenhouse gas than methane? Or C, methane and carbon dioxide are similar in their strengths as greenhouse gases? The answer is a, methane is a more powerful greenhouse gas than carbon dioxide. >> The last session that we dealt with looked at the interaction between the land surface and the atmosphere for many important processes. Now we'll turn to what that land surface looks like and how the vegetation of the land surface is controlled, by climate. And also how the animals affect the vegetation and so on. First of all, we have to realize that the arctic isn't separate from the rest of the world. Of course, it's connected. So the Arctic Life Zone is connected to the Global Arctic Life Zone, and we can think of it almost as part of the mountains because the Arctic ecosystems are very similar, in many ways, to Alpine ecosystems. So if we look at the way the forests occur in the high mountains of the central mountains in the Earth, in the Himalayas and Atlas mountains, the Andes, as we get closer and closer and closer to the North Pole, then the altitude at which the forests occurs comes down and down and down. And when we get to the tundra the forest has disappeared, and also we have a compression of these zones, so just before we hit the tree line, we have a compression of the forest zone, and the alpine zone above it, into a very small vertical distance. If we look at the extent of that area beyond the tree line, it occupies about seven million square kilometers and about two of those are the Greenland Ice Sheet. Later you will hear about the populations, the people of the Arctic, where we talk about the Arctic in a much bigger context. But that includes the peoples that live in forested areas as well. Here, this statistic is about the area north of the forest. The plants and animals and microorganisms in the arctic have evolved over time, of course, to be able to withstand the harsh environments of the past arctic climate. They've been driven, their evolution has been driven by different factors, and for convenience we can look at them in terms of climatic drivers, ground and soil drivers, human drivers, and also links amongst organisms, how plants effect animals, how animals effect plants; how microorganisms effect both of them. And of course all these drivers don't just operate separately, but they all interact with each other, making our life very complicated, trying to understand what is happening. And within each of those drivers, we have many aspects of the drivers. If we just look at one, the climatic driver, you will see that one part of that is temperature. But then, what part of temperature, what aspect of temperature? And we get very surprised when we look at temperature in detail. It can be temperature in winter, it can be temperature in summer, it can be extreme temperatures, extreme events in winter. Or as this graphic shows very surprisingly, even if we have a metro-logical station that's measuring air temperature, the temperature on the ground, where it matters to the plants and animals, is very variable, and quite different from the met station data. So here you see a hillside on the left. And next to that is a thermal camera recording the temperatures there, showing wide ranges in temperature, from the depressions to the exposed ridges. And the temperature profile is much more complicated than we could expect. And remember, this is just one day. What do we do when we look at that complexity over a whole year? It is enormous complexity to deal with. If we now look at the plants that inhabit the Arctic they're about 2200 species they include mosses and lichens and higher plants. One of the characteristics about the Arctic plants is they grow slowly and they're quite short. And they cannot to have been inductive very specifically to the harsh environment of the Arctic but actually grow in places where they avoid it and if we look at how is limited going from the high optic pole of desert through to the semi desert. Through to the shrub tundra, and here you can see shrubs in Alaska, all the way through to the Boreal forest or the Taiga. We can see two things happening. We can see the horizontal extent of the vegetation is gradually increasing from less than five percent in the polar desert to about forty percent in the semi-desert to 100% in the shrub tundra and still 100% arboreal forest as well as that lateral expanse, we have an increase in height as well from very, very low growing mosses and lichens all the way up to trees at the treeline. Now the arctic vegetation has been changing since the end of the last ice age. As you heard in the first lecture, some of the Arctic has remained ice-free for a long time, but most of it was covered by ice 10,000 years ago or more. Many of the species we find in the Arctic now, were actually further south in Europe, North America, or Russia during the last ice age. And have simply moved up, following the retreating ice. If we look at what's happened recently, not over the past 10,000 years, but recently, then we find something rather surprising, and that is that only 37% of the Arctic's vegetation has greened up, has increased in growth over the past 30 years, and this graphic compiled from satellite data. Well satellites interpret light signals and convert that into estimate of plant growth shows that's plant growth is extremely valuable over the last 30 years. Often we don't understand why plant growth in summer not increase when temperature increase. And we don't understand why it has increased in the areas where it has increased, simply because the complexity of the drivers that I explained a little while. But let's look at some examples now. The first is one of change, and quite dramatic change. This is a landslide, sorry, a landscape in northern Swedish Lapland and the photograph taken in 1977 by one of my friends, and again in 2009. And we looked, very extensively at two sites, A4, A3, each of them is 50 meters by 50 meters, recorded all the plants, and looked at the area they occupy. And then we compare them, and we find some very surprising things. That between, sorry let's put it another way. In the last 40 years, the tree species, Birch, that you see here on the green on the right hand side has increased by 600%. Sixfold in those 40 years. And if we look at, we can just see some boulders in 1977. If we try to find them now in the photograph of 2009, we can't, they've gone. So that's an increase in the species that are already growing there. If we now look at something else and we look at the last line that's highlighted, this is the aspen tree, you see that in these two areas it wasn't there 40 years ago, but it's there now. So these are big dramatic changes. Now let's go to Spitsbergen, look at this area on Spitsbergen. Here's a photograph from 1936, a photograph 70 years later, 2008. Nothing's changed. And if you look at the top of these photos, they just cover snow patches. You can see snow patches and even the snow patches are identical at this time of the year after 70 years. What's going on? And the answer is we don't really know. The one aspect that affects the response of vegetation to warming is the sudden extreme events. And these include mid-winter thaws that lead to icing. And that leads to death of animals such as reindeer, musk-ox, and lemmings, and the animals that live on those. If we have one of these events, herded reindeer can be managed, but wild reindeer die. And if we look at these events in one of the few graphics that are available to look at events in this way, we see a box representing ice layers in the snow over a period of 50 years from the subarctic. Each of these ice layers, the red marks, represent a period in winter when the snow thawed because it was warm then it got cold again so that water froze, and it snowed again on top leaving a layer of ice in the middle. If we look at the bottom and see the red lines on the bottom, that meant that in the Arctic winter for a few days, all the snow went, and then the water on the bottom froze when it got cold again, and it snowed on top. And if we look along from 1960 to the year 2000, what we see is these events are becoming more often and they're reaching the bottom of the snow, and that's what kills the animals. Another prediction, another explanation that's very difficult to predict in our models is that very often the way plants respond to climate is indirect via the animals that eat them. Here you see a picture where these little caterpillars that occur in millions about every 11 years in the sub-arctic. They eat whole forests. And you see here dead trees, or defoliated trees. But, there are some green patches, and this is a different species. This is aspen. The dead trees are birch. These little animals open up gaps in the birch forest that can be invaded by a competitor, aspen. Why isn't aspen everywhere? Well the reason for that is moose eat aspen, and you see the trees on the right here, you can see levels two meters where the moose stand on the snow, they can eat the bark off the trees up to a height of two meters, where you can see scars all along these dead trees. So, the caterpillars hold back the birch trees, the moose hold back the aspen trees. What holds back the moose? Wolves. Wolves eat moose. And what holds back the wolves? People. People kill wolves to protect reindeer. So, you see that the interaction between these two tree species is not just a physiological response to climate, it's controlled by an insect, it's controlled by a moose, it's controlled by wolves. It is very complicated. If we now look at the animals a little bit more details, there's about 67 species of mammals. 154 species of birds. But, a number which is really exciting is about 600 million birds migrate to the Arctic each year. But, the biggest group of animals, by far, are the insects. And there at least 3,000 species of insect. The animals that occur in the Arctic either over winter there, in which case they need adaptations, or they move. Some animals move very short distances, from the tundra to the forest in Autumn, then back again to the tundra in spring. Other animals, like the birds, can migrate over thousands of miles. But the animals that stay there, they have to really adapted to withstand the harsh conditions. One little example is the arctic ground squirrel that hibernates. On here, you can see patterns of temperature inside its abdomen where in the winter months, its body temperature going low while it sleeps, it hibernates, and is even getting as low as minus three degrees, which is incredible. And then something kicks in and it wakes up and starts to be active during the summer months. It's a dangerous strategy, what happens if the metabolism doesn't kickstart again? I don't know. The animals that are really well adapted to Arctic conditions are very vulnerable to climate warming. One of the animals which are keystone species, that means a lot of other species are effected by it, is a lemming, very many species are lemming. And they have a characteristic cycle. You can see in the center of this graph. Up and down, up and down, with really high population every four to seven years, and then low population. What is happening to these populations? What controls them? Well, the first thing is, this graphic is not representative of what happened because we're losing these cycles, now. Why? Well, a lot of different things are happening. What controls them. First of all, we have a top-down approach. If we go from the top of the graphic downwards, we see the predators. We see the snowy owl, we see the arctic fox, and then we see something else. We see the red fox moving in, which is knocking out the arctic fox. What happens when the lemming populations are very low? The arctic fox has nothing to eat, then if you see the top line, the arctic fox starts to eat something else. So this is really difficult for us to understand that when the lemming cycles decrease, something that's not connected with it, ground nesting birds, also decrease, and simply because the predators need something else to eat. If we now look at the bottom up processes, then of course the lemmings need food. And that food is controlled by thermaclimate in often quantity and quality. What it also controls the lemming populations is going from the left to the right is the direct effect of climate, so spring climate need the flooding of the borrows that means living on the snow, getting them. Winter climate and I've told you've about the icing event can kill lemming by icing and the summer climate and mainly just affects the food quality. Then there is another factor operating in the opposite direction which are the diseases, and parasites which themselves respond to climate and affect the learning cycles. It is a complex picture, so to understand the future of our biodiversity, we have to understand all of the components, then if we go back to adaptations again, this time look at a really extreme one. Perhaps the ultimate is microorganisms called extremophiles that live in extreme environments, and here you see a section of a rock. It's not bread, it's actually a solid rock, and inside the rock is a green layer of a cyanobacterium. At the landscape scale, if we go back for a sort of review, an overview, then many different changes are expected in life on cold lands. I've described some of them. Here are some more and some sort of summary. We expect a northward and upward expansion of forests and shrubs, even though it's not happening anywhere everywhere. We expect disappearing snow patches and lemming winter habitat, which I've described. We expect the movement north of trees and shrubs along river valleys, which are very sheltered. And that's a fast track, a fast track if you like, for trees and shrubs to get north. As the climate gets warmer and the land dries out we expect more forest fires, more insect damage, even tundra fires. We expect new lakes to form from thermocast pond creation. We expect changes in animals like musk oxen and reindeer from a mismatch between when their food is available and when their reproductive cycles kick in. And for reindeer, we expect forest encroachment onto their traditional grazing lands, both in the mountains and the arctic, so they will have less habitat. This is a complicated picture but that is reality of ecology, interconnections and complications. The next session moves from these complicated processes on land to equally complicated processes in cold waters. >> Which is true? Is it A? There are more insect species in the Arctic than all the plant species. Or, is it B? There are more species of plants than insects in the Arctic. Or, is it C? There are the same number of plant as insect species in the Arctic.
