From Microclimates To Macroclimates

The same factors which affect microclimates, including the plants themselves, translate into larger effects on the heat balance and moisture balance of the earth's surface. In many respects, the macroclimate (over hundreds of kilometers) is the sum total of all the microclimates across broad areas. For example, the local effect of a boreal forest canopy heating up in the sun because it has shed the snow from its branches can make a great difference to regional climate if it occurs on a broad enough scale. When an individual leaf in a rainforest canopy evaporates water and cools itself, this makes a contribution to the heat balance of the whole tree, the whole forest and the whole region. In its own tiny way it also ultimately helps to affect the distribution of heat and water vapor all around the world. So, if anything changes about the average shape of leaves, or size of trees, or the amount of bare ground around the world, this could all add up to a global change in climate.

The sort of way that changes in plant microclimates might scale up to alter global climates was neatly expressed by the "daisyworld" model of James Lovelock (see Box 4.1 and Figure 4.10).

Now imagine that instead the "sun" gets stronger, delivering too much solar energy and tending to overheat the planet. The dark plants will suffer by being

Figure 4.10. The daisyworld model of Lovelock illustrates how the microclimate effects of plants could scale up to global climates. There are black and white daisies which do better under hot and cool conditions, respectively. If the sun gets weaker or stronger, the abundance of the two types shifts according to which does better in their local microclimates (top graph). In the bottom graph, the line "C" shows how temperature would change without the daisies changing their abundance. Line "G" shows how in fact things might change if the white and dark daisies adjust their abundance to exploit the microclimatic conditions: the temperature of the whole planet is regulated by a process that is essentially controlled at the level of microclimates. After Schwartzman, from Lovelock.

overloaded with heat; they not only have to cope with the warm air temperatures but they are also absorbing a lot of sunlight which tends to heat them up even more. In this situation, the dark plants do not grow well and they get pushed out by the white plants that can keep themselves cool by reflecting back most of the sun's energy. As the white plants spread across the overheated planet, more and more of the solar radiation gets reflected back into space, and this cools the climate. Temperature is again brought down towards a more moderate level. It is as if the planet has a thermostat, regulating its temperature to prevent its climate from becoming too extreme.

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Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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