Skip to comments.Millions 'Wasted' Planting Trees That Reduce Water
Posted on 07/28/2005 6:17:29 PM PDT by blam
Millions 'wasted' planting trees that reduce water
By Charles Clover, Environment Editor
Millions of pounds in overseas aid are wasted every year planting trees in dry countries in the belief that they help attract rainfall and act as storage for water, scientists said yesterday.
In fact, forests usually increase evaporation and help to reduce the amount of water available for human consumption or growing crops, according to a four-year study.
Research on water catchments on three continents says it is "a myth" that trees always increase the availability of water.
Even the cloud forests of tropical Costa Rica had less effect in stripping water out of clouds than previously assumed, according to the study, funded by the Department for International Development.
In one part of a large study, Sampurno Bruijnzeel, of the Free University of Amsterdam and one of the world's leading experts on tropical forests, measured the overall amount of water flowing from wet, forested catchments in Costa Rica and found there was no more water than was flowing from surrounding grassland.
While cloud forests were more effective at stripping water out of clouds, the researchers found that the evaporation was higher than on short vegetation.
The study, for the UK's Tropical Forestry Research Programme, will be controversial as it shows that converting cloud forests to pasture does not cause major reductions in water yields.
In India, South Africa and Tanzania, the study showed that plantation forests actively wasted water and were "ineffective" or "counterproductive" at retaining water.
Studies by Newcastle University in the Indian states of Himachal Pradesh and Madhya Pradesh found that planting trees had a "negative" effect on the supply of water.
The study suggests that efforts to convert agricultural land to forest caused a 16 to 26 per cent reduction in water yield. The study suggests that rainfall evaporates up to twice as fast in forests as it does in treeless areas.
Prof Ian Calder, of Newcastle University, one of the researchers, said: "Putting in more forestry in water-stressed catchments where the water table is 500 ft down and the ground water is being mined for uncontrolled crop irrigation will only aggravate matters."
"The public perception is that where you plant trees, you will be increasing the ground water recharge. The evidence is the opposite," Prof Calder said.
Other "water myths" the study knocks down are that trees, particularly plantation trees, are always beneficial in preventing erosion and stopping floods.
Prof Calder said the study showed that there might be some benefit with plantations taking up water in most years, and reducing annual floods, but in major 1-in-20-year floods, the benefits were "negligible".
Thought you guys might like to see this AP report clipping from 2003.
Reagan was right!
Thursday, March 13, 2003
Ottawa Coniferous forests around the world may be emitting more smog-causing nitrogen oxides than traffic and industry combined, suggests a report in the prestigious journal Nature.
The report, released Wednesday, flies in the face of the accepted view that forests reduce pollution by absorbing it a theory Canada relied on in demanding credit for forests as pollution "sinks" under the Kyoto climate change accord.
I hope I didn't give the impression that I didn't think trees could emit pollutants. I just didn't think that they all did.
Leaving the pollen arguement out of it, would you state that all trees emit significant amounts of pollutants?
Trees do emit oxygen also. Isn't it still a net overall good?
Absolutely trees are beneficial. I don't think I'd ever live any place I couldn't go out and walk in them and smell them. They take in CO2, and expire O2 just like you say. Besides that they're a necessary crop for raw materials.
Some give off more VOC's than others. Evergreens give off a lot. A pretty good rule would be the more you can smell the tree the more it gives off. If you go out in the national forests on a hazy day, it is not the big city causing the smog.
I think what Reagan was trying to point out is that human beings are not the cause of all the world's ills. Some things are just beyond our capacity to control and we just have to live with it. Also, he was trying to say we can't regulate our way to a perfect world. EPA tends to think that with just a little more regulation, just a little lower limits, we can get to utopia. That'll never happen.
That's fine about Reagan. As I stated, I don't remember.
But - with all due respect, Google the simple question "Is pollen considered pollution?", and see what you get.
Pollen IS part of pollution, it's just not man-made.
And it's WAY more than "bothersome" for a lot of people.
It is great for stereo stands, tooth picks, picture frames, baseball bats, skis, decks, homes, barns, clocks, chests, etc.
I think the article is pretty strange, myself, but it seems like the qualifier is "plantation trees," which means one type of tree, rather than a natural forest. Like the white pine plantations in your home state.
Anyway, before I make up my mind I'd need to see more on this.
Although I live in the DC suburbs, the back half of our lot is covered in mature hardwoods with typical understory which we don't mess with. We even let fallen trees stay where they fall. Behind our lot is another three acres in similar condition, and the neighborhoon on the other side also lets their trees grow.
The rest of the yards in our own neighborhood are typical suburban lawns.
Our back yard stays plenty cool in the summer, and I can see that rain runoff concentrates in the sward between the trees and our house. Rain in the woods just soaks in.
I'll trust my own eyes over a newspaper article any day.
I have no idea how this affects rainfall, my guess is that it's too complicated.
Indeed, forest land is graded by how much rainfall it receives annually, the best forest land has the greatest rainfall, and supports the fastest forest growth.
Fine furniture, cabinets, gun stocks, outdoor decks...
We have wood falling out of the ground around here.
Yes, I think you're right on target there. Thanks for the comments.
Thanks for the additional comments.
I don't consider something that is biodegradable to be pollution. You and probably a lot of other people do.
Trees make a real mess of things sometimes. They also give off pollen which can bother people. As a kid I suffered from extreme asthma. That's life. I still don't consider something that will be part of the earth in a few months, and help to sustain other life, to be polution. Hey, that's just my take on it.
You take care.
"Really. Which trees don't produce pollen?"
Pollen = Polution? No, I don't think so...
So sez you.
With all due respect, I'm not having the conversation twice.
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