Quantcast
Environmental News for a Healthier Planet and Life

New Forests Planted Near Rivers Could Use up All the Water, Study Finds

Science
New Forests Planted Near Rivers Could Use up All the Water, Study Finds
New pine trees grow from the forest floor along the North Fork of the Flathead River on the western boundary of Glacier National Park on Sept. 16, 2019 near West Glacier, Montana. Chip Somodevilla / Getty Images

By Alex Kirby

New forests are an apparently promising way to tackle global heating: the trees absorb carbon dioxide, the main greenhouse gas from human activities. But there's a snag, because permanently lower river flows can be an unintended consequence.


A study by scientists at the University of Cambridge, UK, has found that river flow is reduced in areas where forests have been planted − and, significantly, it does not recover over time. Rivers in some regions can disappear completely within 10 years.

This, the researchers say, 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.

Age Effect Missed

Planting large areas of trees has been suggested as one of the best ways of reducing atmospheric carbon dioxide levels, because trees absorb and store the gas as they grow, although uncertainties about the strategy persist. Science has known for a long time that planting trees reduces the amount of water flowing into nearby rivers, but no-one had realized how this effect changes as forests age.

The Cambridge 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%.

But 25 years after the trees were planted, rivers had gone down by an average of 40%, or in a few cases had dried up altogether. The biggest percentage reductions in water availability were in parts of Australia and South Africa.

"River flow does not recover after planting trees, even after many years, once disturbances in the catchment and the effects of climate are accounted for," said professor David Coomes, director of the Conservation Research Institute, who led the study.

Published in the journal Global Change Biology, the research showed that the type of land where trees are planted determines the impact they have on local water availability.

Trees planted on natural grassland where the soil is healthy decrease river flow significantly. But on land previously degraded by agriculture, establishing a forest helps to repair the soil so that it can hold more water, and therefore decreases nearby river flow by a smaller amount.

Strangely, the effect of trees on river flow is smaller in drier years than in wetter ones. When trees are drought-stressed they close the pores on their leaves to conserve water, and as a result take up less water from the soil. In wet weather, though, they use more water from the soil, and also catch the rainwater in their leaves.

"Climate change will affect water availability around the world," said Bentley. "By studying how forestation affects water availability, we can work to minimize any local consequences for people and the environment."

Reposted with permission from Climate News Network.

A group of climate activists that have been cycling from the North of the country in stages to draw attention to the climate case are arriving to the Court of Justice on the day that the climate lawsuit against Shell starts in The Hague, on December 1st, 2020. Romy Arroyo Fernandez / NurPhoto / Getty Images

By Julia Conley

Representing more than 17,000 claimants who support climate action, the international organization Friends of the Earth on Tuesday opened its case against fossil fuel giant Shell at The Hague by demanding that a judge order the corporation to significantly reduce its carbon emissions in the next decade.

Read More Show Less

EcoWatch Daily Newsletter

Eat Just, Inc. announced that its cultured chicken has been approved for sale in Singapore as an ingredient in chicken bites. The company has developed other cultured chicken formats as well. Eat Just

As concern mounts over the environmental impacts of animal agriculture, Singapore has issued the world's first regulatory approval for lab-grown meat.

Read More Show Less

Trending

Wildfires are seen burning out of control on November 30, 2020 on Fraser Island, Australia. Queensland Fire and Emergency Services / Getty Images

The world's largest sand island has been on fire for the past six weeks due to a campfire, and Australia's firefighters have yet to prevent flames from destroying the fragile ecosystem.

Read More Show Less
A plane sprays pesticide over the Wynwood neighborhood in the hope of controlling and reducing the number of mosquitos, some of which may be capable of spreading the Zika virus on Aug. 6, 2016 in Miami, Florida. Joe Raedle / Getty Images

By Jessica Corbett

A national nonprofit revealed Tuesday that testing commissioned by the group as well as separate analysis conducted by Massachusetts officials show samples of an aerially sprayed pesticide used by the commonwealth and at least 25 other states to control mosquito-borne illnesses contain toxic substances that critics call "forever chemicals."

Read More Show Less
Prime Minister Jacinda Ardern plants a tree as part of Trees That Count, a project to help New Zealand make a positive impact on climate change, on June 30, 2019 in Wellington, New Zealand. Hagen Hopkins / Getty Images

The government of New Zealand declared a climate emergency on Wednesday, a symbolic step recognizing the Intergovernmental Panel on Climate Change (IPCC) predictions of substantial global warming if emissions do not fall.

Read More Show Less