What Happens to Habitats with Global Warming?

ResearchBlogging.orgAs global warming progresses, habitats change in their suitability for various life forms. It may be that moose will not be able to live in Minnesota in the future; Of the two resident moose populations, the one that lives in the area more affected by global warming has pretty much died out probably due indirectly to the effects of increased temperature. There are regions of the rockies where entire forests are dead because of temperature changes. And so on.

Imagine a large flat landscape. As one moves north vs. south, average annual temperature changes, as does the number of days of frost or the number of days of snow cover. As global warming occurs, the cold/snow lines move north. What could happen is that the organisms that do better in a cooler climate move north. That works for animals, but not so much for plants. But, over time, it is possible that as plants disperse their seeds and compete in different, changing habitats, their distribuitons will also change. When we look at geographically spread pollen spectra from ancient deposits we see this. One can track the movement of oak/hickory forests northward following the last glacial maximum in the central and eastern part of the United States, for instance. Global warming can involve just such a transition.

One problem with global warming is that large flat areas of landscape with large contiguous habitats do not exist in many places. A patch of southern forest in a forest reserve in Arkansas can’t “move” north to central Missouri because the space between them is farmland. The breaking up of large areas of the landscape by agriculture and urban zones makes this process impossible.

Even where that is not the case, the change in climate can be more rapid than the movement of habitats. Even though we can track the oak/hickory line moving north in the US from the last glacial maximum, the post glacial shifts of forest types for earlier glacial involved different dominant species. This is because the rapid climate changes that occur before and after glacial periods does not involve a painless movement of habitats, but rather, the widespread destruction of habitats and their subsequent phoenix like rebuilding.

Indeed, during the Last Glacial Maximum, ecological systems were so heavily disrupted that basic, primary productivity was reduced. There was less life on earth for a few thousand years. If ocean acidity and terrestrial biome disruption, including desertification (which is at an all time non-glacial high at present, or so it would seem) proceeds as currently expected, the basic biological productivity on Earth will similarly drop.

At the moment, human civilization uses up an energy budget equivalent to something like 20 percent of the earth’s biological productivity. If global productivity drops considerably, that can’t be sustained. Yes, folks, those of you who have babies at home now can expect that in the future the child you are raising now will not be able to find food, or possibly even sufficient oxygen. I’m not saying that this is going to happen, but it is certainly a possibility on the table. And, by the way, this is why it is time to stop giving anthropogenic global warming deniers any consideration whatsoever.

But, there is one tiny and, in the broad scheme of things pragmatically irrelevant but scientifically interesting bit of good news. Habitats that are currently extant in alpine region may be less affected than lowland habitats, and may serve as refuges.

The mountain refugia hypothesis is as old as the science of biogeography (more or less) but there is a new paper that explores the question of habitat survival in some detail, in the Swiss Alps.

The paper can be summed up in the following two diagrams, one drawn by me to represent the above outlined dismal scenario for terrestrial biomes, and the other provided in the paper for mountain biomes.


In the first, crude, drawing, each of the two bell curves represent the distribution of various habitats across a spectrum of cooler (left side of diagram) to warmer (right side of diagram) conditions. The first bell curve represents the present, and the second the “after warming” conditions. The overlapping area, with the cross hatching, represents the only common range of conditions. In this scenario, there is a total loss of most of the habitats in the present (left side) and an emergence of mostly new habitats, with only a tiny proportion of organisms able to simply survive in situ. This represents utter disaster that would take millenia to recover from. There will be regions of the world where this is what happens to the habitats in them.

Now look at the diagram from the paper, just published, by Scherrer and Korner:


The density distribution of current ‘seasonal mean’ soil temperatures (‘current’) and in a 2 K warmer scenario (‘future’). ‘Lost’ indicates the micro-habitat temperatures which disappear in a 2 K warmer scenario within our study area, ‘decrease’ indicates the micro-habitat temperatures that decrease in their abundance, ‘increase’ the ones that increase in abundance and ‘new’ the micro-habitat conditions that are warmer than the current warmest temperatures. The arrows indicate the direction of decreasing and increasing micro-habitat temperatures.

In this diagram, we see that there is more overlap between existing habitats and habitats after a warming period. There is some “total loss” and some “reduced habitat” and some new habitats.

This difference, between larger scale habitat loss across vast flatter landscapes and changes in mountains, is due to the scale of variation. In mountain regions, habitats are more variable, and more importantly, variable in a smaller physical space because of the effects of altitude.

If you start near sea level in a temperate habitat and go north, you’ll reach a boreal habitat in a few thousand miles. If you start in the same exact habitat and go up a mountain side you will reach a boreal habitat in tens of miles or less, but going to a higher elevation. This allows for more different habitats to exist side by side in a small space. This, in turn, allows more shifts of habitats without entirely losing one habitat or another. The paper by Scherrer and Korner defines the extent and nature of this variation, focusing on surface temperature as the main variable.

Our results demonstrate that the topographically induced mosaics of micro-climatic conditions in an alpine landscape are associated with local plant species distribution. Semi-quantitative plant species indicator values based on expert knowledge and aggregated to community means match measured thermal habitat conditions. Metre-scale thermal contrasts significantly exceed IPCC warming projections for the next 100 years. The data presented here thus indicate a great risk of overestimating alpine habitat losses in isotherm-based model scenarios. While all but the species depending on the very coldest micro-habitats will find thermally suitable ‘escape’ habitats within short distances, there will be enhanced competition for those cooler places on a given slope in an alpine climate that is 2 K warmer. Yet, due to their topographic variability, alpine landscapes are likely to be safer places for most species than lowland terrain in a warming world.

We need to avoid making two mistakes when considering the results of this research. First, variation in habitat across altitude does not clone variation i habitat across latitude. No matter how high you go up on a temperate or tropical-zone mountain, you are not going to reach a place where the sun sets for six months (at the polar circles). Rainfall patterns are important and are determined by a number of factors including several that will not vary across altitude. The mimicking of latitude shift with altitude shift is the product a talented but imperfect mime.

Second, mountain habitats are small and vulnerable. A single pathogen, a major storm, a very bad year for rain, etc. can wipe out a large area which can be re-inhabited from adjoining areas. But isolated mountain habitats do not have adjoining areas from which organisms can migrate or disperse. So if you were thinking that you could relax about global warming, sorry, no dice. Indeed, some of the “lost” habitats in the diagram supplied with the paper may be among the most unique and irreplaceable, such as periglacial biomes in temperate or tropical regions. Such biomes may re-evolve, but they will be very gone and unable to “come back” in any other way once all the glaciers melt off all of the temperate and tropical mountains.

Scherrer, D., & Körner, C. (2010). Topographically controlled thermal-habitat differentiation buffers alpine plant diversity against climate warming Journal of Biogeography DOI: 10.1111/j.1365-2699.2010.02407.x


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13 thoughts on “What Happens to Habitats with Global Warming?

  1. Do they take the soil composition into account? Some plants are very specific in their soil requirements. The soil further north can be the same temperature and altitude with the same rainfall, but with the wrong composition. I would also think that different soils would be affected differently by warming.

  2. Soil is very important. Over large scales, some of the differences in soil would actually track climate given enough time. Mountain soils will tend to be variable, but also lacking in certain types that are found in lowlands, so plants requiring those would do poorly with or without climate change. But yes, that’s a very good point, and no, they only covered temperature in this paper.

  3. One concern I’d have, in addition to the general smallness (and subsequent fragility) of mountain habitats, is the extent to which they may be reliant on glacial melt for their water supply. The paper may have considered this, of course, but I’d have thought that the retreat (or complete disappearance) of water supplies might well result in the destruction of a high proportion of the habitats that would otherwise be able to survive by moving upslope.

  4. is the extent to which they may be reliant on glacial melt for their water supply.

    Yes! The periglacial habitats would simply not exist if there are not glaciers!

    That also affects things way downstream. In Tibet/Nepal, this is a major factor for many human communities as well. If the snow falls as rain and there is no reservoir effect, the riverine ecology is totally different.

  5. “In Tibet/Nepal, this is a major factor for many human communities as well”.


    I think the human consequences of climate change are sometimes under-discussed. Poorer populations don’t have the ‘insulation’ from the environment modern technology has given First Worlders, so any changes will likely impact them much more severely — water supplies and food growth (subsistence farmers lacking the infrastructure for irrigation) being much more dependent on the vagaries of rainfall, and furthermore these areas usually lack good preparation from natural disasters (both in the organized-preparation-and-evacuation aspect, and buildings are not usually built so sturdily) so large scale changes in rainfall might harm these people severely (either by droughts leading to famine, or by floods causing damage and loss of life more directly). Also, heat waves are known to kill people in poor health without access to air conditioning.

    It’s kind of insidious, since most of these things wouldn’t cause (unlike, say, murders or car accidents) deaths that could be traced directly to climate change, but there could still be increased rates of harm and death.

  6. Here in Maine, we can thank global warming for the huge increase in fleas and ticks. These creatures are finding our neck of the woods to be a much more suitable habitat than in years past. The snow melts a bit sooner and the first frost comes a bit later now, it seems. We worry about our pets & children in regard to the increase in lyme disease here.

  7. Climate Change Impacting Worldâ??s Most Vulnerable Nationâ??s Fresh Water: World Leaders at Economic Summit and UN Climate Talks Urged to Act

    Preeminent climate scientist and noted environmental leaders speak out on behalf of the Kiribati Nation, calling upon world leaders who will gather this month at the Economic Summit in Seoul and U.N. Climate talks in Cancun to address the issue of water scarcity and its impact on food sources. James Hansen, world renowned climate scientist, Lester Brown, Founder and President of Earth Policy Institute, Rabbi Warren Stone, religious environmental activist who served as delegate at the U.N. climate talks in both Kyoto and Copenhagen and Kathleen Rogers, President of Earth Day Network, call for bold action to alleviate this and other manifestations of global climate change.

    Preeminent climate scientist and noted environmental leaders speak out on behalf of the Kiribati Nation, calling upon world leaders who will gather this month at the Economic Summit in Seoul and the U.N. Climate talks in Cancun to address the issue of water scarcity and its impact on food sources. James Hansen, world renowned climate scientist, Lester Brown, Founder and President of Earth Policy Institute, Rabbi Warren Stone, religious environmental activist who served as delegate at the U.N. climate talks in both Kyoto and Copenhagen, and Kathleen Rogers, President of Earth Day Network, call for bold action to alleviate this and other manifestations of global climate change.

    Dr. James Hansen warned: â??Kiribati and the Micronesian Islands epitomize the global warming story: actions now have effects decades in the future. It is now too late to avoid small sea level rise wiping out some Pacific islands, but we can and must avoid wiping out the land and lives of hundreds of millions of people and species.â?http://www.columbia.edu/~jeh1/

    Rabbi Warren Stone, who will soon be attending a world religious leadersâ?? Spiritual Forum in Seoul, relayed: “The most vulnerable nations of the world, particularly Kiribati and the Micronesian Islands, are currently facing a severe crisis of water shortages and the resulting disappearance of their food systems. Within decades, many other nations will be facing these same water and food issues. The Micronesian Island nations are the world’s first environmental refugees. It is the moral responsibility of world leaders, both at the Economic Summit in Seoul and the UN climate talks, to act now to protect future generations and the worldâ??s creation from climate devastation.â? http://www.templeemanuelmd.org/aboutus/staff/rabbi_stone/

    Kathleen Rogers, who will soon be attending the U.N. climate talks in Cancun, urged: â??In the absence of a global agreement on climate, our leaders must turn the COP 16 into a referendum on funding to protect developing nations from the disabling and destructive impacts of global warming. Anything short of full funding will seal the fate of not just Kiribati and the Micronesian Islands, but other at risk nations. It leaves the developed nations defending their economies and way of life at the expense of millions of people and species.â? http://www.earthday.net/node/63

    Lester Brown, Founder and President of Earth Policy Institute stated, “If we continue with business as usual, how much time do we have before we see serious breakdowns in the global economy? The answer is, we do not know,because we have not been here before. But if we stay with business as usual, the time is more likely measured in years than in decades. We are now so close to the edge that it could come at any time. For example, what if the 2010 heat wave centered in Moscow had instead been centered in Chicago? In round numbers, the 40 percent drop from Russiaâ??s recent harvests of nearly 100 million tons cost the world 40 million tons of grain, but a 40-percent drop in the far larger U.S. grain harvest of over 400 million tons would have cost 160 million tons.” http://www.earth-policy.org/

    About Kiribati
    Kiribati, a Micronesian island of roughly 100,000, sits precariously on the very front lines of climate change. Located in the Pacific Ocean, Kiribati straddles the Equator. The tiny nation is composed of one island and 32 smaller atolls, islets of coral, which circle a lagoon. In 1999, two Kiribati islets, Tebua Tarawa and Abanuea disappeared underwater. Another of Kiribatiâ??s islets, Tuvalu, has lost its coconuts trees, a major food staple, because the seawater has salinated the fresh water sources. The United Nations Intergovernmental Panel on Climate Change predicts that the sea levels around Kiribati will rise by about half a meter (20 in) by 2100 or earlier due to global warming and that a further rise is inevitable. It will be the first nation of the world to disappear completely.

    As Kiribati falls victim to climate change, we are reminded that one of the most urgent issues of our day is access to fresh water. Pacific Ocean waters are increasingly encroaching onto and salinizing the island. Salt water is seeping into the ground soil, destroying both the edible crops and the fresh water table underneath the island that has sustained its inhabitants and all life forms for centuries. The drinking water procured from streams and rains is also becoming salinized. The island people must now either import water and food for their families or become refugees leaving their nation.

    The ravages of climate change are already impacting the Kiribati nation in frightful ways. Minister of the Environment of Kiribati, Michael Foon, addressed delegates at the UN Copenhagen talks: â??Our children have no water!â? How many more of our children will die because they have no access to fresh water?â? Jesse Lambourne, a Kiribati native, spoke passionately: â??We do not want to lose our homeland; we want to live in our country, our country called Kiribati! They tell us to leave the coast and leave our homeland. If our whole country is coastal area, where do you move? Our land is our spiritual connection to our ancestors, our culture, our memories â?? we are fighting to maintain our land as a people.â?
    Lambourne closed with this personal plea: â??Help us, help us, tell the world our story!â? The Kiribatians offered each delegate a shell necklace from their island and asked that they be remembered.

    Hansen, Brown, Stone and Rogers join in response to the Kiribati plea and call on world leaders to act with a sense of urgency and moral purpose. â??Remembering Kiribatiâ? means awareness of the larger threats of cultural annihilation that climate change will bring to the most vulnerable. Climate change will present us with the most fundamental moral challenge that humanity faces in our century. It is imperative that we recognized that now is the time to address global water and food issues and develop international management programs. They urge all world leaders to review the technical papers on climate change and water at http://www.ipcc.ch/pdf/technical-papers/climate-change-water-en.pdf.

  8. I’ve been watching these comments blip on and off as they are posted and deleted. Why are global warming deniers such babies? Does this commenter really represent the What’s Up with That site?

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