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Thread: Response to Plumberkhan's adaptation to climate change question...

  1. #1

    Response to Plumberkhan's adaptation to climate change question...

    Sorry... long response.

    I’m not sure were to start off on this topic. Ecologists can’t predict the future, but we can generate possible scenarios based on past and current events. These scenarios, in many ways, are reliable because we have duplicated some of them in both laboratory and field experiments and have a decent understanding of our natural history. The complexities of situations are what cause ecological phenomena to vary in their deterministic nature and difficult to pin-point with accuracy. We can predict with accuracy ranges of conditions and the probabilities that they may arise, but not which one will definitely occur and, if it does, at what intensity/size/level. Basically, when ecologists speak about the possible impacts that global climate change will have on ecosystems we are using our knowledge of past and current events in the same way that detectives use past and current criminal profiles to match up with a suspects behavior to help understand and predict that suspects behavior before he does something. We know this works because Law and Order and CSI always catch the bad guys.

    Our current distribution of ecosystems and their associated biotic communities are a result to the geological and climatic events of the Pleistocene. There were a number of warming and cooling periods during this period (lasted more than 2 million years I believe) and the current species that are occupying the earth are survivors of the abiotic and biotic influences of the glacial advance and retreat cycles. Current North American migratory bird behavior may be linked to this because birds can fly over large tracts of unsuitable habitats in search of refugia. Migratory bird adaptations can be viewed in two ways: an adaptation to exploit resources in newly unglaciated areas or as an attempt to escape harsh northern winters. We don’t know and it’s probably a combination of the two. Wood warblers are a classic example of animal adaptation to the climate changes during the Pleistocene. My field, canid ecology (i.e. wolves, foxes, coyotes), has been in the process of being pieced together. Birds happened to get the most attention first. We happened to kill just about all the wolves and couldn’t study them early on.

    Anyway, the record of vertebrate biogeographic migrations during the past 125,000 years indicates movements of considerable magnitude in response to changing temperature and moisture regimes during the glacial advances and retreats. The freezing of the Bering Strait allowed not only humans to invade North America but also beavers, sheep, musk ox, caribou, elk, moose, bison, brown bears, and gray wolves (coyotes and red wolves are N.A. evolved). It also allowed some North American animals, such as deer, goats, pronghorns, horses, and camels to cross over. Freezing and thawing allowed a considerable amount of migration and reverse migrations to occur.

    So, we know our past and can match ecosystem changes to variations in climate as evident in paleontology and geology. Current ecologists are studying current climate conditions and current ecosystem responses to them and comparing them to what we know in the past. Although situations differ, we can find generalized trends that are commonly shared between events to help deduce mechanisms that drive these changes. The area of concern is how temperature and precipitation affect ecosystem processes such as net primary production, decomposition, and nutrient cycling that effect the distribution and abundance of species.

    There are a number of current and ongoing research experiments that look at the possible effects of global climate change on types of ecosystem processes, such as Free Air Carbon Dioxide Enrichment (Duke University), International Tundra Experiment, U.S. Forestry Service’s Inventory and Analysis Program, and the Harvard Forest Experiment.

    Harvard ecologists (Harvard ecologists > Harvard doctors on environment issues :D ) have been manipulating temperature and moisture levels in the soils of the Harvard Forest by placing heating cables in the soil and using irrigation. What they have found is that increasing both soil temperature and soil moisture, forested ecosystems increase soil respiration by almost 50% through increased microbial and root activity and increase carbon concentrations in the organic layer of the soils. These trends are similar to those found in hotter and more humid areas of the world. This also has a positive feedback because increase rates of decomposition and microbial respiration leads to significant rise in emissions of carbon dioxide from the soils to the atmosphere. However, we are not sure of larger and long-term effects.

    To see what effect this would have on community structure a similar study was done in Colorado in a mountain meadow. The ecologists surrounding a meadow with electric heaters to alter the timing of snowmelt that caused rises in soil temperature and soil moisture. The result was drastic changes in the meadow herb community that caused pollinators and small mammal communities to collapse. Within a few years the meadow became dominated with shrubs and small trees.

    So, as one can see, this has been a step-by-step process by ecologists to understand how climate variation influences ecosystem processes via a number of experiments. First, ecologist noted that the distribution and abundance of plant and animal species can be plotted as a function of mean annual temperature and rainfall. Next, they went into the field and tested this in a number of ways and confirmed it. The step they are taking now is to extrapolate from past events, current trends, and our current understanding of the mechanisms to interpret possible scenarios via environmental change.

    One practical way that non-ecologists can use to understand this effect is to hike up some of your local mountains. Temperature and precipitation change as you go up in elevation, similar to going up in latitude. On the mountain ranges around Phoenix and Tucson Arizona you start out in a desert vegetative zone with cacti and climb up to a taiga like vegetative zone with spruce. No different if you walked from Arizona to Vancouver. These high elevation areas served as a refuge for cold weather organisms during the last glacial retreat. That’s why Arizona has Canadian like species. At one time, they were down there. This is the same all throughout the Rockies and Appalachians.

    How does all this gibberish tie into the question about species adaptability? Well, that’s what I’m trying to build up to.

    Wildlife ecologists or wildlife biologists, doesn’t matter because both are the same, are interested in quantifying how animals allocate their time among requirements for foraging, sleeping, moving, breeding, and so on. These are what we call activity budgets (or time budgets). This conceptual framework helps us understand the relationship between time allocation and survivorship, reproductive success, body condition, and other aspects of species natural history. This stuff is very analogous to economics. It’s why ecologists and economists fight like cats and dogs. We’re basically siblings and everybody is caught in our sibling rivalry. What we need is for the general public to step in and kick both of our asses and set us straight so that we can deal with real issues and stop trying to out-debate the other.

    Anywho… like economists studying the market, ecologists assessing animal energetics assume that the goal of an animal is to maximize its net energy balance. Neurological and physiological capabilities of the animal itself link it to its environment (the glorious free market, if you will). So, the environment is not just were an animal exists, it has a functional and dynamic relationship with the animal.

    Thermal energy is a relationship the animal has with its environment’s climate through radiation, conduction, convection, and evaporation. Each of these methods of thermal exchange change relative to one another as the animal’s environment alters: Rain, wind, and other abiotic factors effecting energy exchange over the short term. Changes in plant cover are one of the influences on energy exchange over longer periods of time.

    The ecological metabolic rate is the expression of the energy (cost of living) for the purpose of daily activities and other physiological processes. Metabolic rates vary from one activity to another and from one species to another (smaller species have higher metabolic rates due to core:surface area ratios).

    To bring the two together, time-energy budgets (TEB) are formed. First, you develop an activity budget. Then you convert activity data collected to energetic equivalents from estimates of energy costs for each activity as determined from controlled experiments or the literature. Then you can compare these estimates with the animal’s daily activities and their costs to mortality, survivorship, and reproduction. Finally, you compare these to population and ecosystem processes. Now ecologists can go ahead and building both phenomenological and mechanistic models to help us understand patterns and processes that we see in nature and how changes (especially man-made) influence these patterns and processes.

    So, how does all this tie into Plumberkhan’s question? It depends on the species. For a wildlife ecologist like me that has studied a generalized and wide ranging predator like wolves and coyotes… global warming… who cares. Our species and its prey (typically ungulates) are so wide ranging they are very adapted to multiple ecosystems whether natural or man-made (Rome has wolves living within its city limits). We’ve got wolves in the Artic and the deserts of NM and AZ and in northeastern coastal region of NC. However, snow leopards and polar bears are another story. Wildlife ecologists who study highly specialized species are shaking their heads and thinking what a mess.

    All-in-all, we are all very concerned to the effects. Largely because the majority past extinctions and range expansions occurred gradually and species that went extinct were replaced by similar species with the same role. Today, that is not the case because species are disappearing and not being replaced. It’s equivalent to removing engineers and plumbers from our society. Who’ll maintain our town sewage and sanitation? It’s the same for our ecosystems; however, they’re much more complex and interdependent. There are ways that these living systems compensate, but overtime and with enough losses without replacements we are starting to feel effects.

    In any case, global climate change will not be uniform. Some areas will get colder, others warmer, and others won’t change. Overall, there will be more warming trends than anything else. Some animals will do well, others won’t, and many might not be effected. This is basically what history says. What ecology has done is help us develop a list to narrow out species that we know will be affected. Specialized animals with small isolated ranges, low reproductive values, and very narrow diet breadths. Basically the same credentials a species needs to be potential candidate for the endangered species list.

    It also important to be asking is how is this going to affect agriculture. The forecasts are rosy in some sectors and not others. Climate and weather are the key factors in growing crops and not technological advances, crop varieties, and irrigation. This is the point of the Environmental Change Unit out of Oxford University, to figure out what regional and global trends will be seen in agricultural sectors. Domestic crops have the same needs as wild plants and exhibit environmental tolerances. Most crops will benefit from carbon dioxide concentrations but it varies based on the crop. Cotton may increase up to 60%, wheat up to 10%, and cereal crops up to 5%. However, we should prepare for shifts in geographic ranges of crop species. With 1% increase or decrease in temperature the entire corn belt in the U.S. will shift either north or south. Ditto for rice in Asia. Shifting agricultural zones will have significant economic, political, and social costs. It took centuries to establish these areas and there is not reasonable explanation that we will invent some technological solution for a quick rebound. It’s assumed the mid-Atlantic developed nations will have positive effects to the warming but developing nations around the equator will have about a 10% decline. They’ll get increased temperatures but not increased moisture to offset the stresses that crops will face.

    This is just the plant species. We have no idea as to the effect on the pollinators needed for the reproduction of these crops. We are already feeling the decline in European honeybees. USDA is already planning to switch to Africanized (killer) bees and is tolerating Africanized hives used to pollinate crops. The agriculture ecologists are certain that a significant drop in bee colonies throughout the world will reduce crop production significantly (I’m not sure of the number).

    This has gotten long and I’ve got work to do. Hope this was helpful… or more confusing.

  2. #2
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    Apr 2003
    Wow, that was interesting...thanks a lot for writing it finlee.


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