Friday, June 6, 2014

Ecosystem Sciences Part 4: Climate Control

In the previous part of this series we saw that ecosystem provides us various goods like food and drugs. We focused more on discovery of new foods and drugs. I plan to write an entire part on how ecosystem services are important to agriculture a little later. Right now, lets turn to the second type of ecosystem service – Regulating.
The most well known regulating service is climate control. It was not really so popular till a few years ago, when it started to fail in its job. As a rule in this series, I am not writing about how we are destroying the ecosystem, but focusing on what it does for us. But I will make an exception for the climate, because it is a widespread concern, and a good example of how we don’t realize the value of ecosystem till it begins to fail.
First thing to learn about climate is that it has been literally tailor made by our ecosystem, especially the biosphere (biosphere, as you know, is made up of all living beings on earth). Billions of years ago, when the earth was young, there was no oxygen in our atmosphere. It was dominated by nitrogen, CO2 and methane. We would have found it rather difficult to breathe in this paleoatmosphere, as it is called.
Some of the early living beings, called cynobacteria, started using CO2 to make food and release oxygen. In 2 billion (200 crore) years, the oxygen levels rose to current levels or even higher. This made it possible for animals like us to evolve and survive.
Other than oxygen, the most important ingradients of the atmosphere are the Green House Gases (GHG). Yes, you read it right. Green house gases are supposed to the villains. But they are not. They are just like the good guys in movies who get exploited beyond limit.
A lot of energy from the sun falls continuously on earth’s surface. It should usually hit the surface, bounce and vanish in the vast space. This is what happens on most of the other planets. But not on earth. The green house gases (like CO2, methane, water vapour and ozone) absorb the energy that comes packed in infrared rays in sunlight, and emit it in form of heat. This is why the average temperature of earth’s surface is about 14 ⁰C. If the GHGs did not do this, the surface temperature of our earth would be a freezing -19 ⁰C, which would be a good thing for the makers of warm clothes and heaters, but a certain disaster for life in general.
What this means is, if the amount of green house gases in the atmosphere goes up, it will absorb more heat from sun rays. So the temperature of earth will go up. Our ecosystem has stabilized the green house gases and thus the temperature for hundreds of thousand of years. CO2 is a major green house gas. Scientists have found data of CO2 concentrations in atmosphere for the last 450,000 years. It shows that the concentration has always been between 200 and 300 parts per million, or 0.02 to 0.03% for all this time. Oxygen breathing creatures release CO2, agriculture frees up a lot of CO2 from land, natural events like volcanoes and earthquakes also fume large quantities of the gas. But the trees and plants absorb the CO2 from atmosphere. The vast oceans dissolve vast amounts of it. Thus the ecosystem keeps the CO2 in atmosphere nearly constant. Or so it used to keep, till around 70 years ago.
Since 1950, man started burning fossil fuels with particular enthusiasm. Fossil fuels- like coal, oil and gas- emit CO2 when they burn. Additionally, man started cutting down forests in a big way. Deforestation releases CO2 in two ways – the carbon stored in the plants is released as CO2, and the carbon stored in the land also frees up. The emission of CO2 went up very quickly to very high amounts. The ecosystem tried its best, in fact, the absorption of CO2 by trees, plants and land went up substantially in last 20 years. But it is not enough, there is no way ecosystem can absorb all this extra CO2. As a result, the concentration of CO2 now stands at 400 parts per million, higher than any time in human history.
The surface temperature of earth is increasing as a result of increase in CO2 in atmosphere. So far, the rise is mainly in the temperature of ocean. In the last 100 years, the average temperature has gone up by 0.8 ⁰C, and by the turn of this century, it is expected to rise by a further 2.4 ⁰C.
We might not worry about such small changes in our room temperature, but when the average temperature of entire earth goes up, it is a very large scale change. Some of the bad things that are expected to happen are – rise in ocean levels, food and water scarcity, large scale flooding, acidification of oceans and resulting death of marine life and extinction of many species.
This is the story of the climate control ecosystem service, or rather its failure. It might be failing now, but it has been working quietly for hundreds of thousands of years, till we decided to push it to its limits. In the light of this grim knowledge, we might be able to better understand the regulating service I cover in next part – Flood Control.

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