Having posted that above, I want to go into the matter of what Designs has been posting about, which is that humans do have an effect on the earth, and sometimes it is a massive effect.
One thing that humans do effectively is to dig up raw materials from the earth, transport it elsewhere and then bury most of it somewhere nearby. Entire mountains of elements are being relocated from one continent to another this way. If I were an alien that came from elsewhere to observe the processes of the planet, I would suspect that the purpose of humans was to speed up the transport of matter to move it faster than geological processes.
Those dead trees in the SoCal mountains were mostly killed by beetles which were able to infect the trees because of drought. I lost a few trees to the beetle, and what would happen is that as long as the tree had a good water supply the beetle could not infect it. But if it dried out the beetles could drill under the bark and consume the inside layer, which killed the tree. I was able to water the surviving trees and keep the beetles away. Some details about the tree plague are here. http://www.forestdata.com/deadtree.htm
One of the massive human changes on the earth that fascinates me, is nearby and I went to go see a couple weeks ago is the Salton Sea. It was formed over a century ago when irrigation from the Colorado river flooded and water that would normally flow into the Gulf of California in Mexico started to fill a large basin in California that was below sea level. It took a couple years to control the flooding and by then there was a a large lake in the basin. It gets replenished by agricultural runoff, and is saltier than the ocean. For many decades in the 1950s, 60s and 70s it had marinas and was quite a recreation zone within a short distance of Palm Springs, offering boating and sport fishing. But something happened on the way to paradise and the salinity level went up, algae blooms would occur and they would die, consuming oxygen, which led to fish die offs. The resulting stench and shores littered with dead fish bones killed off the desire for recreation there. The one benefit is that it is a stopping ground for migratory birds, but as a whole it is a monument to the sometimes folly of human tampering with the earth.
