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Local water availability is permanently reduced after planting forests:
River flow is reduced in areas where forests have been planted and does not recover over time, a new study has shown. Rivers in some regions can completely disappear within a decade. This highlights the need to consider the impact on regional water availability, as well as the wider climate benefit, of tree-planting plans.
"Reforestation is an important part of tackling climate change, but we need to carefully consider the best places for it. In some places, changes to water availability will completely change the local cost-benefits of tree-planting programmes," said Laura Bentley, a plant scientist in the University of Cambridge Conservation Research Institute, and first author of the report.
Planting large areas of trees has been suggested as one of the best ways of reducing atmospheric carbon dioxide levels, since trees absorb and store this greenhouse gas as they grow. While it has long been known that planting trees reduces the amount of water flowing into nearby rivers, there has previously been no understanding of how this effect changes as forests age.
The study looked at 43 sites across the world where forests have been established, and used river flow as a measure of water availability in the region. It found that within five years of planting trees, river flow had reduced by an average of 25%. By 25 years, rivers had gone down by an average of 40% and in a few cases had dried up entirely. The biggest percentage reductions in water availability were in regions in Australia and South Africa.
Partial river flow recovery with forest age is rare in the decades following establishment (open, DOI: 10.1111/gcb.14954) (DX)
(Score: 0) by Anonymous Coward on Friday January 31 2020, @07:27AM (3 children)
I've been told that California's oaks in particular hold a lot of water under ground. I actually got to see this first-hand when a rather small (and it turns out hollow and somewhat diseased) oak was cut from an unsuitable place between my house and another. Well into the month of June, and even July I observed water in the hollow of the stump. This doesn't sound like a big deal unless you realize that it's normal for us not to get any rain during those months, and we didn't. All that water was coming up from the root system. The poor thing did start suckering from the stump--a lush oak bush, but we'll just have to whack that back eventually because it's a bad spot for an oak. It may just die on its own--those burly bushes are susceptible to disease. I had one on another stump that died from powdery mildew after an unusual early Summer rain. There's some attrition on oak saplings I guess. The big oaks were unaffected.
(Score: -1, Offtopic) by Anonymous Coward on Friday January 31 2020, @02:19PM (1 child)
Yeah and besides that, I've heard the maples aren't too happy with the large oaks to begin with.
(Score: 0) by Anonymous Coward on Friday January 31 2020, @07:11PM
Aw geez moderators. Come on! What, was it too soon?
(Score: 0) by Anonymous Coward on Friday January 31 2020, @03:07PM
When I cut down an overgrown magnolia tree and pulled the stump out, there was a puddle of stinky water directly under the stump. The roots had found a leaky water meter 20 feet away.