- This week I would like to introduce Professor Jack Williams, who was born in Chicago, Illinois, and attended University High School in Sacramento, California, where he later went to pursue his bachelor's in geology at Oberlin College, to finally obtain his PhD in geosciences at Brown University. He came to Madison in 2004 and is here today to talk about the ecological responses to climate change since the last Ice Age. Please join me in welcoming Professor Williams to Wednesday Nite @ the Lab.   (applause)    - Great. Thank you all. It's really a pleasure to be here. I do have degrees in geology and geosciences, and if you're paying attention, I'm now a professor in geography, which has confused my family to no end. They can never quite remember which geo am I on any given day. But the reason for that is, as you'll see, that I really do a fairly interdisciplinary kind of work. I study species responses to climate change. So ecology, climatology, using the geological record and using the sediments we can find in the many lakes and mires around us, as archives of past ecological and climatic history. So that opening slide there gives you a bit of a sort of taste of the scales that we're going to be working on. Looking from the last Ice Age, 21,000 years ago, the last glacial maximum we call it, where we had ice sheets sitting over North America. Right here where we stand was under ice. And then those ice sheets retreat, and, as temperatures rise, as CO2 levels, carbon dioxide levels in the atmosphere rise, various species move north. And so one of the things that we use as time period quite a bit for is studying ecological dynamics in a warming world, which has obvious comparisons to what's happening today.  So sort of a four-part, four-chapter structure here. Give a bit of an intro first here, then move into understanding a bit more about how we use the past to gain insight into ecological dynamics and make preparations for what's happening now and is expected to happen in the future, give an overview of some of the key lessons we've learned along the way, and then finish a bit on this crossover from paleoecology, which is the field of study that I'm representing here, to conservation biology, how do we make informed management decisions given this kind of information from the geological record.  So, to start with and to give an overview of if you think, again, sort of this context of a changing world, rising temperatures, rising carbon dioxide concentrations. Carbon dioxide now at 400 parts per million, which we haven't seen since the Pliocene, and it's still going up. So if we then think about the fact that we expect temperatures to rise and other kinds of climatic changes to go with that, we then start to ask how we best conserve species of concern, biodiversity, ecosystem services, all kinds of things that you might want to adapt and manage under these changing climates. And, in ecology, we can think of some general areas of risk that might come with those changing climates. So the first one is habitat loss, that if there are species that are endemic to, dependent upon, the best competitors in, highest rates in population and transit growth, other certain climate regimes and those climates disappear, then we'd expect those species to maybe shrink in population size, perhaps even be at risk of extinction. Sometimes this is called the top of the mountain problem or the polar bear problem because polar bears are very charismatic species that are dependent upon arctic sea as a key habitat, and as that arctic sea ice melts back, there is concern about polar bears having their habitat diminished. No one actually thinks, as far as I can tell, that polar bears will go extinct, but we do think that they'll have reduced population sizes and so forth.  Then we have fast rates of change. How, if climates change quickly, if there are rapid rates of temperature rise over the coming decades, and the scenarios being, say, two to four degrees Celsius temperature rise over this century, that's pretty fast, the question becomes, how quickly can species keep up? And so there, at the far right, as you can see here, is some different estimates of rates of, let's see, if I look at my cursor there, so we have these different bars here representing the rate of dispersal ability or mobility of different species. How far can they move in sort of typicals, or populations, kilometers per decade? Some species can move quite far. The large animals have high mobility. Some species, the trees, can't move at all. They have to throw propagules out and reseed and move that way. So they don't move as fast. And then the various lines there represents spatial rates of climate change. Converting these estimates of temperature change in any given area to how far will thermal zones move laterally. If you're a tree, if you plant trees, you may look at Arbor Day and their maps of plant hardiness maps, those plant hardiness zones are expected to shift as temperatures rise and species will need to move to keep up with those shifts. There's also the question of rapid and abrupt changes. So the first point to there was fast climate drivers and can species keep up. There's also the question of fast ecological responses. Will species respond non-linearly? Where are the tipping points? And so this idea that there might be multiple stable states represented conceptually by those balls there. And that you might have one stable state, like a grassland, and then you might push a system hard enough that it flips another state, like a forest. So there can be sort of back and forth between these states. Down in the lower right there, we have different parts of the world. That figure looks a little washed out from here, but that's a map of the world. And those colored areas are different regions of the world where we have observed system dynamics in the past of these sort of abrupt shifts. The Saharan Desert in Africa, North Africa, shifting pretty quickly back and forth, doing a grassland state and a desert state. The North Atlantic circulation flipping on and flipping off, speeding up and slowing down. There are some parts of the Earth's system that seem to show this kind of bi-stability, these quick flips in state.  And then the part that I have actually worked the most on, and I'll develop all these a bit more as we go forward, but the part that I've worked on the most, and will develop the most here, is this novelty challenge, sometimes called the bottom of the mountain problem, where, at the top of the mountain, if you sort of look at that cartoon there, that cartoon is supposed to represent sort of thermal zones, cold blue, so cold at the top, warm is at the bottom, and in a warming world those thermal zones move up-slope, that those coldest environments at the top move off the top of the mountain and disappear, which is bad news for those species. But the bottom of the mountain has warmer than present conditions than has ever been seen at that mountain before. So now there's new climates that have not been seen at that location before, and the question becomes, how will species behave or respond to those warmer than anything seen at present conditions? Or, I'm focusing on temperature here, but there might be other dimensions of climate. More extreme precipitation regime events and so forth. This is called novelty, and there's a map and right there, sort of mapping out globally, areas of high climate novelty. This is a paper we did about 10 years ago now. And we did a sort of analysis of 21st century climates by the end of this century versus climates at the beginning of the century and identified places where the climates of the future had no close counterpart in the climates of today and they tend to occur in the tropics and subtropics. The warmer world and those parts being at the leading edge of a warming world becomes a question of how well can we predict how species respond to climates that are warmer than anything we see at present?  So that's the set up. And these are all kinds of questions that are ecological questions today and, not coincidentally, they are ones that can be addressed by looking at the past. And that's a big part of what I do in my work is trying to work with geological data and the geological record of past climatic and ecological events and draw parallels and insights into what's happening today. So in this picture here, what we're seeing now is changes in temperature, on the vertical axis, and this is expressed as relative to the late 20th century, like 1960s, 1990s or so. And positive values will be warmer than that reference point. Negative values will be cooler than that reference point. And the time scale is a little tricky here. It actually changes its scaling, and this line here, if I get my cursor back, represents today. This is looking out 100 years in the future. This is looking back over the last 150 years. So this would be back to about 1860 or so. This is basically the domain for which we have weather station data, instrumental data, direct observations of the climate system and its change through time. And what we see is that there's been a rising trend in temperatures with some little stair steps along the way, and we expect these trends to continue. And this is being driven by the rising greenhouse gases from our fossil fuel and land use and land cover change through the emissions of greenhouse gases, carbon dioxide, methane, and nitrous oxide, primarily. We go further back in time, we can see there's been some variations back here, but you can see that over this time scale we've had a range of variation of plus or minus a degree or so but nothing like what we expect to see over the next century. And this is now going back to about 10,000 years ago. So this is now back to 2,000. This scale is changing here and back to about 10,000 years ago. So this is a common challenge we face. And I'm focusing on ecology but you could sort of extend this challenge to any area of the world. How do economic systems behave? How will flood regimes in the greater Milwaukee area behave? This general challenge, we're moving the system to a state that's not like anything we've seen in recorded human history and how do we best adapt and plan. So in this challenge, we have sort of, if you're a scientist t  Okay, but this isn't a paleoclimatology talk. This is an ecology and biogeography talk. So this is really the structure that, as an ecologist, we're working in. What we're interested in less is what's causing these climate variations, but how do species and ecosystems respond to them and survive them because if you're a species that's been around for any more than a few hundred thousand years, you've had to live through multiple glacial and interglacial cycles and you've had to be able to adapt to and accommodate this kind of climate change in the past. So now what I'm going to do is zoom in into just one of these events. That's the best study of them all because have lots of lakes and mires and radiocarbon data of sediments that cover it. And so this is the last deglaciation. This is the last transition from the last glacial maximum to the current interglacial, what we call the Holocene. So now we're looking, time is now going that way again. Oldest, 22,000 years ago, to present at far right. Timescale or vertical scale again is temperature as difference from present. So this is a record from Greenland. So this is telling us that Greenland was about 10 degrees colder than present about 20,000 years ago. And that about 10,000 years ago, it reached more or less modern day or pre-Industrial Revolution temperatures, and it's been more or less constant there ever since. And what you can see is, of course, you can notice very quickly that it's not just a little linear ramp up. There's some very abrupt changes along the way. There's some distinct events, and we have given them names. We call that first abrupt warming the Bølling warming, as part of a broader event called the Bolling-Allerode. And then there's that Younger Dryas, which is that return to sort of near glacial conditions. And then the abrupt end of the Younger Dryas, which is the start of the Holocene, the start of the current interglacial. So lots of things are happening climatically. Globally, temperatures rise by about four to five degrees Celsius. Some of those changes aren't what we would-- Sometimes you hear geologists say, "Oh, things happened really fast in the past." And people say, "Oh, yeah, you're a geologist, "you're talking about millions of years, that's not meaningful." These are really abrupt, even on human timescales. People think basically it's Greenland and other high resolution records that some of these abrupt shifts in the climate of these areas could have been nine to 14 degrees Celsius in one to 40 years. In our own lifetimes would have been sort of the comparable kind of rate of changes. So these are big past climatic events, these aren't global. These are North Atlantic, western Europe. But in these areas, at least some regions, we've had very rapid changes. Ice sheets melt back over this time period. That plotted upper right is showing this, I think, this really beautiful diagram of the Laurentide Ice Sheet and the Cordilleran Ice Sheets. The dark blue is its furthest extent, and then it's melting back over this sort of from about 19,000 years ago to about 6,000 years ago. The ice sheets are wasting away as temperatures rise. Sea level rises because that water has got to go somewhere and it winds up in the world's oceans. So that's about 400 feet or so of sea level rise from the last glacial max to the present. And then novel climates emerge. And what I mean here by novel climates is that if you actually look at the ranges of climates that occurred at some points in the past to the ranges of climates that happened today, there are areas of non-overlap. And the way to kind of show that visually is at that far right plot there, where what we're looking at here is just two simple temperature axes: summer temperatures and winter temperatures. And we're looking at that each location represents some location in North America for three different time periods. Red, being a projected   (inaudible)   set of climate model simulations for what we think North American climates might look like maybe 30 or 40 years from now. Black would be the lat  We've already walked through this point, the idea that that was at one site and then we can sort of step back and look at the continent and see that species accommodate climate change by moving. They try to stay within their thermal zones of their climatic optima or ranges of tolerance, and one way they do so is by moving spatially as the environments change around them.  Moreover, I've only been showing you spruce, mostly because it's a nice kind of iconic one, but if you actually were to look at other taxa and start to look at how they respond, what you start to see is that different species respond to different rates and in different directions. And so we can see that that spruce again, northwards shift. We look at ash. Ash doesn't really move much of anywhere. It expands a little bit north. There's a bit of a northern range to it. But mostly what ash does, it goes from being not very abundant to being really abundance, between 15,000 and 13,000 years ago, and then not being very abundant again. And so it's a completely different trajectory from what we see from that sort of simpler story of sort of northward expansion with rising temperatures. And notice that today we think of spruce being up in Canada and northern Wisconsin and ash being parts of southern Canada and the eastern deciduous forests. So we think it'd be used as largely disjunct species from different biomes or ecosystems. But if you've been an ecologist walking the landscapes 15,000 to 13,000 years ago, you would have thought that spruce and ash were just found as a normal association. And so the mixtures of species change. What we start to mean by novel communities, or reshuffling in novel mixtures. As climates change, each species follows its own path. And as a result you get this mixing of and breaking down of exiting community around you and new ones emerging. We should expect the same sort of things happen in the future. We should expect that because of this, some of these co-evolutionary relationships should be pretty weak. If your neighbors are changing all the time, maybe you're not tightly co-evolved with the other species around you, and so we're starting to think about some of those implications for co-evolutionary relationships. And, again, this sort of prediction question. Another point that's, I think, of real interest is that if you actually look at the last 1.8 million years, even going further back, one thing you don't see a lot of are species extinctions. Species extinctions are there. They're not nothing, but they're not very common either. And you can make a good case and they not much above, back to what a sort of typical background rate, species are kind of always coming and going and that might be sort of typical. And when you do see extinctions happen, they often tend to be at the cold periods. That sometimes species die out either locally or regionally during the cold glacials but not as much evidence of extinction during the warm glacials. So there's some sense that there's a bit of asymmetry here where the colder periods are more special for species and can drive extinctions more than the warmer periods. This is sometimes called the Quaternary conundrum there because I just showed you a few slides ago these predictions of large rates of 15% extinction rates over this century in response to 21st century climate change, and yet, when we look at the geological record, we just don't see that much of it happening. But the obvious counterexample to that, I've been focusing mostly on plants so far, but there was these very large animals roaming these landscapes, we used to have mastodons all over the place around here, and those mastodons aren't here anymore. The mammoths aren't here, the camels aren't here, the horses, all over North America. And, worldwide, we do have a major extinction event, but it's very much concentrated on the big animals. We lose about two-thirds of all the big animals worldwide starting about 45,000 years ago up until the recent past. In North America, we lose about 34 genera and this long-running question about what doesn't end. And I'm of the personal mindset that it is some combination of climate change and human dispersal, right? Humans are moving out of Africa beginning around 100,000 years ago or earlier, they spread into Europe, into the southeast Asia, into Australia by about 40,000 to 50,000 years ago, into the Americas by about 15,000 years ago. And, interesting  Okay, so we see this idea of novel ecosystems that I talked about. Species, and I'll show in a moment, a good case he made that these novel communities are forming in part to response to the novel environments that they encounter that exist in the past that don't exist today. And one way of looking at this, going back to this point about seasonality, remember what I  showed you at far right there, that 15,000 years ago climates in the past were more seasonal than they are today. Now look to the far left and look at where ash is found today. And that middle plot here, I don't know how well you can see it, but there is this black set of dots and, maybe a little harder to see, a set of gray dots here. This is the climate space of North America. And what this figure should be showing is that we have, the black dots is where ash is present in North America. The gray dots is where ash is not present but those climates exist. And then, for much of ash's range, we have some constraints that ash cannot be found in these areas. We don't find ash in these areas at least. But over here ash is right up against the edge of the North American climate envelope. It's found right in the middle of North America, which is as seasonal as it gets in North America. So there's some sense that ash could expand into these climates, these more seasonal in terms of climates, if those were to exist. They don't exist now, but these climate models suggest that they did exist in the past. And so some of these sort of spruce, ash assemblages, and some of these other no analog communities that formed we think are forming in response to this heightened climate and temperature seasonality of this sort of late Pleistocene time period.  So one consequence then, as I showed you-- Oops. I don't have-- Oh, yeah, so I showed you a map a few moments ago about oak, I'm looking at how oak does. This is another map for Fraxinus. This isn't quite as clean as the other one I showed you ago. But, again, here's the modeled distribution of ash 15,000 years ago. We take that model, predict it forward to present, and the model basically thinks that ash shouldn't exist at present or should exist only at very low abundances. Where, in fact, we know that ash does exist at present. And so this is a good-- And the correlation between these two maps is terrible. It's, you know, 0.09 correlation. And so this is a good example where the model is not matching to the data. It's having a hard time taking these novel climate phases of the past and then basing predictions on them into the climates of today and the species of today. 

 Just like that oak plot, we saw that, in general, predictions based on more recent time periods do better, predictions based on earlier time periods do worse, but now, if we look down here, the correlation, again, is very low. And so, basically, if you-- What this is telling us is if you take the set of climates that we know for 14,000 years ago and the known distributions of ash from 14,000 years ago, build a predictive model based on this data and relationships, that model has little or no predictability to today. And so that is an example of how these novel climates can confound these models because, again, they're statistical models. They're not very good at extrapolation into the unknown. This is a case where they're really breaking down in these sorts of situations. And one more just kind of visualizations around this, this is showing the sort of total climate space of North America 15,000 years ago, the total climate space of North America 1,000 years ago, and then the black dots being the places of high ash abundances. And so what you can see is this portion of climate space that opens up down here is also a place where we're finding lots of ash. The ash is really preferentially occupying these highly seasonal climates, these climates that don't exist today. And so, again, this is sort of these signals that as climates change and new portions of climate space open up, species are able to respond to and occupy these spaces and are sometimes our ecological forecasting models have a hard time predicting these novel climates and community responses to them. Okay, so those are some of the lessons, some of kind of the big kind of things we can take away from what we see from the geological record. And now just a few slides at the end about what should we do. What kind of things can we-- We take this information and bring it to bear on current challenges. In general, if you're thinking about climate change and you're sort of working at a high level thinking about sort of policy options, there's sort of two general options. One is mitigation, which you try to mitigate or prevent climate change by reducing our greenhouse gas emissions. And the other one is adaptation, where you try to increase our resilience to climate change. When I first came into the field, you know, 20 years ago, adaptation was viewed as kind of a taboo, that we shouldn't be thinking about adaptation, we should be really focusing our efforts on mitigation. But increasingly, these are seen as not either/or, it's and/both kind of situations because you want to avoid the really high end climate scenarios that might cause a four-degree or five-degree warming this century that would cause all kinds of harm to low-lying areas, small islands, heat waves, you know, droughts, etc., and, you know, rates of adaptation for species and so forth, you want to avoid those outcomes, and mitigation does that for you. It moves you away from the high- end climate change scenarios down to the lower end or middle end climate change scenarios. Whereas, adaptation recognizes that climate change is already underway, climate change is happening. It's been underway for the last several decades. And now it's just a question of how much climate change we'll have, and at what point we'll level out or maybe start to reverse things. And so the Paris Accords said we need to stay at 1.5 degrees Celsius. So that would put a limit around here or so. So there's different scenarios and pathways to get there, but no matter what there's going to be some amount of climate change and some amount of adaptation needed to those. And so adapt to what you can't avoid. And so if you think about, from an ecological perspective, one thing to recognize is that, again, species accommodate climate change by moving, but that's actually been sort of a hard concept for us. We have legal restrictions in place. We think about invasive species, there's some species you can't move across certain boundaries. And I'm certainly not advocating for wholesale movement of species across continents. We know about  This gets in this topic of managed relocation. And so sometimes if you're worried that a species habitat will entirely disappear or largely disappear as a result of climate change, maybe due to sea level rise or other factors, moving these vulnerable populations, picking them up from one place to north. This, again, can cause concern. I tend to be of the perspective that this is a natural process, it's just one that we haven't seen happen much because we haven't see that much climate change happen in our human lifetimes. And so this is the kind of thing I tend to support as a way that's congruent with past climate change and past adaptations to it.  And also recognize that what we think of as a normal or natural set of species around us may be a temporary phenomenon. Species move, associations come and go, and then as climates change we should expect these shifting associations to happen in the future. Some species moving faster than others, some species being more temperature sensitive or rainfall sensitive or extreme sensitive, and so we'll expect to see this reshuffling of species. This has led to this concept of novel ecosystems, and there's a bit of an argument about that right now. And there's a couple of quotes about that argument. And so Hobbes, for example, is arguing that novel ecosystems, the concept of novel ecosystems is based upon the fact of novel ecosystems. He's saying already we can see that some ecosystems have departed entirely from their historical analogues. Whereas other have argued, no, no, no, we can keep things in a current state. We shouldn't sort of wave the white flag of surrender, but accept these unavoidable and widespread irreversible changes. And so there's been an argument about this. What should we be conserving to? What should we be maintaining? I, again, tend to favor more of the former perspective. That these are dynamic systems that are systems in changing and we should look for ways to facilitate those changes, one that best promotes biodiversity and the services that we depend upon.  And, again, we expect that climates are changing, we expect novel climates over the century. So this is very much a real process for us all to be wrestling with. We are wrestling with in the professional sector and I think it's worth bringing out to the broader community as well.  And if we look around, I've been focusing here on climate change, but if you think about it, there's, of course, all kinds of other factors transforming these ecosystems. There's been invasive species. There has been land use and legacies of past land use. So the Parthenian rangelands is an example of a toxic, you know, invasive species that we generally try to limit its spread. Puerto Rico is an example of an area that was widespread sugar plantations, is now reforesting. And as it's reforesting, it's becoming this interesting blend of native and exotic species, apparently with, you know, not major negative ecosystem or biodiversity consequence. If anything, biodiversity may have gone up in some of these areas with this mixture of natives and exotic. Isle Royale is being a relatively pristine area but one that nonetheless is changing in many ways. And the corral triangles as an area that is changing and is threatened by rising temperatures, ocean acidification, and so forth. And so we can recognize that the world is changing, we can recognize that novel ecosystems are emerging. Some of these we might view as more positive than official, others we might view as more negative or ones to try to reverse, but, nonetheless, we should recognize that we are in this changing world and that we should seek to facilitate certain kinds of change and mitigate or reverse others. Okay, so that's, I've kind of worked through these points here already. But, again, this perspective that comes out of paleoecology of the world has always been in flux. Now new changes are happening. We are accelerating the rate of change. And, in general, I would say that prudence would dictate that we try to slow down rates of climate change, we try to stabilize the climate system, but we should also accept that change is underway and that those rates of change lead to adaptation needs, and those adaptation needs can be grounded in the lessons from the past. Thank you. Thanks a lot.   (applause)