It’s become common knowledge that when humans cause deforestation, it’ll be bad for the environment. This new study is another proof that we should take care of our forests better, as deforestation is linked to less rain in tropical rainforests.
Published in the journal Nature, this study found that large-scale cutting of trees in the Amazon and other rainforests could raise the risk of wildfires, promote irregular precipitation patterns, and surprisingly, lead to declining agricultural yields.
When forests are strong and thriving, they help produce rainfall in a process called moisture recycling. It’s when trees absorb rainwater and release its moisture back into the atmosphere, which leads to cloud formation and consequently more rain.
When humans disrupt this process through deforestation, the impact is far-reaching.
Moisture can travel up to an average of 373 miles before falling as precipitation. In some areas of the Amazon, for example, up to 70% percent of rain could come from the forest-driven cloud formation. When those areas are deforested, they’ll face arid, harsher climates.
Lead author Callum Smith said, “When we’re removing trees, we’re making the environment drier and that lack of moisture that’s the big cloud above those trees just disappears.”
In this study, the researchers assessed precipitation and deforestation patterns in the Amazon rainforest, Congo Basin and Southeast Asia (Indonesia, to be specific, a country which hosts the Leuser Ecosystem). They used satellite data from 2003 to 2017.
After looking at the data, they discovered significant drops in average rainfall in each of these regions. The impacts were visible even on small scales, but the most dramatic changes could be seen over wide areas.
For instance, at the scale of about 15,500 square miles, scientists found that rainfall decreased 0.25 millimeters per month for every percentage point of forest loss.
Moreover, the researchers identified a link between rising human activity and decreases in local rainfall.
Significant loss and the damage so far
According to Bernardo Flores, an ecosystem resilience researcher at the Federal University of Santa Catarina in Brazil who wasn’t involved with the study, this study provides further understanding that deforestation reduces rainfall, which reduces forest resilience and increases the risk of tipping points and negative impacts on local economic activities.
Like Flores, many other experts have said that the Amazon is approaching a “tipping point” that will result in drier conditions, turning its leafy vegetation into a savanna. Of course, this would threaten the wildlife in the Amazon rainforest which could be vital in combatting climate change in the future.
The Amazon is one of the most biodiverse places on Earth, home to one in ten of the planet’s known species. We all know that it’s been dubbed “lungs of the planet” due to its capability to process massive amounts of carbon dioxide per year.
Despite what we know and some efforts to prevent more loss of rainfall, we are seeing some dangerous changes already occurring. For example, the dry season in the Southern Amazon is now four to five weeks longer than it was in 1970.
“Once we deforest, we lose one of our greatest natural defenses in protecting ourselves from climate change. This is not only true for forests, but also other ecosystems,” said Robin Averbeck, forest program director at the Rainforest Action Network.
Reforestation: it isn’t that simple
One of the most common solutions that people give when they talk about deforestation is: plant more trees. While planting trees can help, the reality is not that simple.
In the Congo Basin, for example, much of the forest loss is due to poor, small-scale farmers trying to survive.
According to Frances Seymour, senior fellow at the nonprofit World Resources Institute, it’s important to distinguish corporations and governments engaging in deforestation practices from local communities who are trying to make a living. So, socio-economic factors are also important and should be put into consideration.
Besides, trees don’t grow instantly like in video games. It might make us feel better when we donate or contribute to projects that aim to plant, say, a hundred thousand trees. However, research from the UK Centre for Ecology & Hydrology showed that a lot of these trees don’t survive long-term.
It is true that in some tree-planting project sites, survival rates were high when the reforestation attempt is done with the right approach. But in most cases, the projects simply plant trees and leave them alone afterwards.
Leaving the trees to “grow naturally”
Regions in tropical and sub-tropical of Asia have been favorite spots for restoration projects, therefore the international scientist team examined those areas. Per the team, this research is the first to bring together data to evaluate the long-term outcomes of restoration projects.
The team analyzed tree survival and growth data from 176 restoration sites where natural forests have suffered degradation. They found that, on average, 18% of planted saplings died within the first year, rising to 44% after five years.
However, survival rates varied greatly amongst sites and species, with some sites seeing over 80% of trees still alive after five years, whereas at others, a similar percentage had died.
According to co-lead author Dr Lindsay Banin, the survival variability could be due to a number of reasons, such as planting densities, the choice of species, the site conditions, extreme weather events or differences in management and maintenance, as well as local socio-economic factors.
“Success is very site-dependent—we need to understand what works and why and share that information, so we can bring all sites up to the level of the most successful and harness the full potential for restoration,” Banin said.
The research added that there’s likely no panacea to this problem, and restoration should be tailored to local conditions. Banin said, “This will help ensure the scarce resources and land available to restoration are used to best effect.”
So… should we be careful about restoration projects?
I think we should, yeah.
I’ve seen this happen more than once from where I live: people from private to government sectors sharing their tree-planting projects, then they’ll just leave them alone with absolute minimum or zero maintenance. The saplings died out, dried out, and then they got removed for other projects unrelated to planting trees.
So maybe, what we can do before supporting is make sure that the project is long-term, catered to the locals, and with proper maintenance. The UK Centre for Ecology & Hydrology study found that active restoration provides faster results than simply letting nature take its course.
Project sites that included tree planting activities gained forest cover more quickly than sites which were left to regenerate naturally.
The team also found that many studies simply tracked the fate of planted trees rather than structural properties of the whole community. They believe that both types of data should be combined in the same study areas, so it’ll be easier to determine acceptable levels of mortality that will still deliver a return of forest cover.
They also added that more experiments are needed to help hone the most appropriate and cost-effective methods of restoration across sites under different conditions. “This is why assessing restoration outcomes over the long-term, and gathering information that helps to maximize success rates, are so important. We need the focus to shift away from simply planting trees toward growing them and helping our forests thrive,” said co-author Prof Robin Chazdon.
According to co-author Prof David Burslem, “The study also provides a warning, to protect our remaining forests as much as possible, both because restoration outcomes are uncertain and to provide the diverse seed sources needed for restoration activities.”
Nonetheless, reforestation is still important
The findings of these two studies could be a great motivator for efforts to reduce deforestation done by governments and big companies.
We still need our forests, particularly ones which are carbon and biodiversity dense. In recent decades, we’ve seen major deforestation in rainforests only, with forest cover reducing by an estimated 32 million hectares between 1990 and 2010.
So hopefully, the findings and the fact that we should pay attention to the planted saplings can lead us to better reforestation projects in the future.
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