Quantcast
Environmental News for a Healthier Planet and Life

Help Support EcoWatch

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.

People Have the Power - VOTE 2020

Climate-action nonprofit Pathway to Paris first launched in 2014 with an "intimate evening" of music and conversation after the People's Climate March in New York City.

Read More Show Less

EcoWatch Daily Newsletter

Heo Suwat Waterfall in Khao Yai National Park in Thailand. sarote pruksachat / Moment / Getty Images

A national park in Thailand has come up with an innovative way to make sure guests clean up their own trash: mail it back to them.

Read More Show Less

Trending

The 2020 presidential election poses a critical test of climate conservatives' willingness to put their environmental concerns before party politics. filo / Getty Images

By Ilana Cohen

Four years ago, Jacob Abel cast his first presidential vote for Donald Trump. As a young conservative from Concord, North Carolina, the choice felt natural.

But this November, he plans to cast a "protest vote" for a write-in candidate or abstain from casting a ballot for president. A determining factor in his 180-degree turn? Climate change.

Read More Show Less
Headquarters of the World Health Organization in Geneva amid the COVID-19 outbreak on Aug. 17, 2020. FABRICE COFFRINI / AFP via Getty Images

The World Health Organization (WHO) announced Monday that 64 high-income nations have joined an effort to distribute a COVID-19 vaccine fairly, prioritizing the most vulnerable citizens, as Science reported. The program is called the COVID-19 Vaccines Global Access Facility, or Covax, and it is a joint effort led by the WHO, the Coalition for Epidemic Preparedness Innovations (CEPI) and Gavi, the Vaccine Alliance.

Read More Show Less
Exterior of Cold Tube demonstration pavilion. Lea Ruefenacht

By Gloria Oladipo

In the face of dangerous heat waves this summer, Americans have taken shelter in air conditioned cooling centers. Normally, that would be a wise choice, but during a pandemic, indoor shelters present new risks. The same air conditioning systems that keep us cool recirculate air around us, potentially spreading the coronavirus.

Read More Show Less

Support Ecowatch