Posted on 07/28/2005 6:17:29 PM PDT by blam
Millions 'wasted' planting trees that reduce water
By Charles Clover, Environment Editor
(Filed: 29/07/2005)
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".
Astounding ignorance. Trees make good firewood or wood pulp.
"A suprise to me."
Another thing people are surprised to hear, and still don't believe, is that trees are a source of pollution.
Reagan got bashed and still gets bashed for pointing this out.
But it's true.
Several things come to mind. First, the water run-off from large forests wouldn't be especially great, because the water is held in the undergrowth. While there isn't great run-off, there is a bountiful amount of animal and plant life supported by the water in these eco systems.
On the one hand the study says that trees don't create more rain, but then it also notes that there is greater evaporation from the forests. This makes one wonder if the people running the study understand where rain comes from.
"Some trees", not all trees...
Water attracts trees, not the other way around. Some people just don't think logically.
"Another thing people are surprised to hear, and still don't believe, is that trees are a source of pollution."
I remember a childhood trip to the Smokey mountains where a park ranger explained that the haze in the air was from the trees.
Yup. I remember that. (Reagan's picture still hangs over my desk)
It would seem to me that if there were not enough water.. trees wouldn't grow.
Besides.. this was a FOUR YEAR STUDY? How freepin stupid is that? Four lousy years... don't they know how long trees live? I'm sorry, but I don't care how sophisticated your computer models are, you cannot measure/predict the impact of a forrest on a complex ecosystem in just four years.
The good Lord just doesn't work that way... or that fast.
Really. Which trees don't produce pollen?
Since most trees root systems are on the top 3-6 inches of the ground this study proves that some people get far to much time and gelt to spew their ignorance. In the rain forests of South America, nearly the whole eco system is above ground.
Trees provide the canopy to cool the air by shade and evaporation..causing all that water to go into the air and return as rain..maybe not in that area, but it comes down. The Sahara desert once had forests. After they became extinct the desert was the result.
The biggest polluter on earth is forest fire. Forest fire releases carbon, not only from the fire itself but the ground. And it continues to release that element for years untill a new forest grows. Fire also releases Mercury as well as other elements collected over the years on the ground. So lets get Bruce "The Rabbit" Babbit to get out on another photo op of him with a drip can lighting up a "controlled" burn...the ignorant idiot!
Um, not much survives a 20 year flood. This is overstating the obvious, and ignores the benefit of having trees reduce erosion, which would conserve valuable topsoil.
Some of us learned that in basic Environmental Science merit badge class at summer camp..
He is still lampooned for his comment. He was taken out of context for political reasons and they still run with it.
"Trees provide the canopy to cool the air by shade and evaporation..causing all that water to go into the air and return as rain..maybe not in that area, but it comes down."
Of course, but that wasn't the point of the study.
And water vapor is a greenhouse gas much more powerful than CO2.
I don't consider pollen to be polution. When Reagan addressed this issue, I believe he was refering to some trees which produced a fair amount of oxygen and others which net drains on the oxygen supply.
Millions of allergy sufferers would disagree - as would the kind folks that came up with the term "pollen count", as part of the pollution index.
But everyone is entitled to their opinion, to be sure.
And I couldn't speak to what Reagan was actually referring to - though if he was referring to pollen, he would've been more widely understood, and also correct.
I would suggest that Reagan wasn't talking about pollen. If he had been, he wouldn't have qualified his comments about 'some trees'. He would have said all trees.
As for the pollen count, the inclusion of it in the daily index reporting doesn't make it pollution. It does make it bothersome for people with allergies, which is why they report it.
Thanks for the additional comments.
When Reagan menthioned trees in this manner, he was talking about overall polution in our big cities. (At least I think he was.)
I didn't mean to imply that oxygen was a polutant, but that Reagan's premise was that some trees could compete with humans for the oxygen supply in heavily populated areas.
Thought you guys might like to see this AP report clipping from 2003.
Reagan was right!
Associated Press
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...
mmmmmmmmmmmm, wood!
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.
Cheers.
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