New environmental threats generating more greenhouse methane into the earth’s atmosphere
Article by S. Tom Bond, Retired Chemistry Professor & Resident Farmer, Lewis County, WV
Those of us who follow the science of global warming realize it is not a simple thing. It involves many phenomena. It involves some that are very important but are far from everyday concerns, such as the currents of the ocean. Many more keep turning up. Here are a couple that are new.
Deserts everywhere have a “biocrust” or Biological Soil Crust, sometimes known as microbiotic crust. We tend to think of deserts as places which have few or no plants, and hence no life. Not so, biologists tell us. In time, even the most arid areas develop a layer of life from one eighth of an inch thick to several inches thick. They are valuable to consolidate the surface and prevent soil from moving in wind and as a result of occasional rains. Unfortunately, biocrusts are rather delicate compared to soil cover by vascular plants.
Biocrusts are composed of complex mixtures of cyanobacteria, moss, lichens, bacteria and fungi. They are driven by photosynthesis and rare rains. They have the ability to desiccate (dry up completely) and come to life again quickly when a rain occurs. They remove carbon dioxide from the air and replace it with oxygen. They fix nitrogen from the air, and support further growth, in part by securing necessary nutrients from the arid soil and by binding sand grains together. Perhaps one of the most important attributes from the human point of view is they reduce or prevent dust storms.
The composition of biocrusts varies from place to place on the earth’s surface, and by different soil conditions in any local area. They are vulnerable to trampling. A footfall may take 10 years to recover, and much longer, up to 250 years where it is very dry. Now, as scientists who study them are finding out, changes in temperature and rainfall also jeopardize them. They are a global warming problem in the western United States and from the high latitudes to the Sahara and Ecuador.
A good short article about biocrusts in Arizona in particular is here.
Pictures of biocrusts are here and here. The second has two videos of how desert mosses can turn green in less than a minute when they are rehydrated by rain or pouring on water! The fuzzy object in the foreground of the second is an eyedropper, and you can see the individual plants!
The second threat of our article is methane release from melting permafrost. You may have heard of that before, but it is a continuing and increasing concern. Human carbon dioxide release depends largely on burning hydrocarbon fuels, although some other industrial scale processes also release it. This is directly attributable to intentional human activity.
Methane has an industrial component also, due to leaks in production, which increases with greater use of methane for fuel. However, the biggest worry is uncontrollable natural release from melting permafrost. Permafrost is the layer of frozen earth characteristic of the far north and a few other places where the temperature has been below freezing most of the tine. For a map of location see here, click on small map to the right for an enlargement.
The area of permafrost is huge, about 24% of the ice free land area of the northern hemisphere. Entrapped in this frozen earth and water is vegetation, which slowly rots and produces methane in the absence of air, and methane rising from the deep toward the surface is trapped here, too, since the beginning of the last ice age, 25,000 years ago.
The first reference in this section has in the middle of the page two graphs, one of the average annual temperature at a selected point in Siberia in red and a second of Bonanza Creek, near Fairbanks, Alaska. Much of this area is thawing, releasing the methane. The Arctic is warming twice as fast the Equatorial Region.
The worry is what is called “positive feedback,” an uncontrollable forward change in a process which results from the change itself. In this case, warming causes methane to be released and even more, uncontrollable warming, out of proportion to the human activity.
This article states that methane equivalent to 205 gigatons of carbon dioxide could be released by the melting of permafrost. This alone could contribute an extra half degree of warming, according to a study it mentions. This is a low estimate compared to some that are out there.
Here are pictures of holes in permafrost, most of them the result of escaping gases. The prospect is horrifying, both for the residents where it occurs but looking forward to the future of a hot earth with many consequences!
| Time (yr) | Permafrost depth |
|---|---|
| 1 | 4.44 m (14.6 ft) |
| 350 | 79.9 m (262 ft) |
| 3,500 | 219.3 m (719 ft) |
| 35,000 | 461.4 m (1,514 ft) |
| 100,000 | 567.8 m (1,863 ft) |
| 225,000 | 626.5 m (2,055 ft) |
| 775,000 | 687.7 m (2,256 ft) |
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