A tree is probably the most iconic image of environmentalism. Or better yet, a person planting a tree. We are called tree-huggers by some people, after all. It has long been known that trees are key organisms in our ecosystems - they sequester carbon dioxide (CO2) and release oxygen, they provide food and habitat for many species, and they reduce erosion and flooding, to name just a few of their many important functions. Trees are amazing and we definitely want them around. However, in face of climate change, trees are believed to take up CO2 and produce a cooling effect on the earth, but that is not always true. It may sound crazy, but in some circumstances, planting trees can actually do more harm than good. The reason may be something simple such as planting trees that are not the right tree species being planted in the right ecosystems. Or if they’re being planted in areas like grasslands and disrupting those naturally treeless ecosystems. It’s all about location, location, location!
Tree planting initiatives are becoming more and more popular, especially as carbon offsets or “carbon credits”. Several tree planting initiatives are on the go in North America, like the Nature Conservancy’s Plant A Billion Trees campaign and Forests Ontario’s 50 Million Tree Program, and there are similar programs all over the globe. Corporations, brands, and companies are jumping on the bandwagon as well, investing in tree planting projects as a way to work towards being carbon neutral. In Canada, the government recently announced that they are committing to a project of planting 2 billion trees by 2050 to reduce greenhouse gas emissions. Now, that’s a lot of trees! And what’s that famous quote again? “With a great amount of trees, comes great responsibility.”
Planting trees is not a simple environmental fix and has great potential to put our ecosystems and people in danger if it is not done properly. It’s time we started understanding all sides of this story, so we know what type of tree planting and other restoration projects to support going forward.
The Role of Trees in Climate Change
Climate change is being driven by greenhouse gas emissions - CO2 being a significant one - and the planet is warming, ice is melting, sea levels are rising, and extreme weather events are becoming more frequent and severe. Trees are known to be a solution against climate change because they take in CO2 and release oxygen during photosynthesis, which typically produces a net cooling effect for the climate. This means trees are a carbon sink - they hold onto carbon and prevent it from being released (until they are chopped down or die by other means). And tree lifespans are very long, naturally speaking; they can live for several decades and even centuries for some species. Given they aren’t cut down, trees can be fairly safe places for carbon to stay. This is why it seems so obvious to plant more trees to suck up more CO2 and cut down less to reduce CO2 emissions.
Source: Know Your Meme
Nothing is ever as simple as it seems though, especially in nature. Forests do not always produce a net cooling effect because of a little thing called albedo. Albedo is the measure of how much solar radiation (heat and light from the sun) can be reflected off of a surface. Darker colours absorb more radiation and lighter colours reflect more. That is why my old black car with leather seats and dysfunctional air conditioning was killer to drive on a hot, summer day. Since it had a black surface, it absorbed a lot more heat and was essentially a sauna on wheels. Similarly, darker coloured land surfaces, like forests, absorb more solar radiation than lighter ones, like grasslands or snow. So, forest cover can actually warm the climate in some regions of the world. There is a complex and delicate balance between the warming and cooling effects of forests, and the net effect can vary depending on where the trees are.
An accredited study from 2007 suggested that the best region to plant trees is the tropics because trees grow fastest closer to the equator and, in those regions, they have the ability to take in the most amount of CO2. Planting trees closer to the poles, in colder environments where it’s snowy, is likely to cause a net warming effect. And in the in-between space? Well, planting trees in temperate regions, like Canada or the UK, might produce a neutral effect as the cooling and warming is likely to cancel out in many cases.
Dr. Christopher Williams, geography professor and researcher from Clark University, is working on some of the latest research on reforestation, and he said the following: "If we fail to consider both the carbon and the albedo effects, large-scale tree-planting initiatives, such as Canada's 2Billion Trees Initiative and The Nature Conservancy's Plant a Billion Trees campaign, could end up placing trees in locations that are counterproductive for cooling the climate system … It is all about putting the right trees in the right place."
Problems with Plantations
“You can’t plant a forest; you can only plant a plantation,” said journalist Ted Williams, in an article on the harms of reforesting, and I think this statement says it all. Forests are entire ecosystems - trees are only one part of the whole complex system. It would take a lot more time and effort to create a full, natural forest from the ground up than it does to plant a tree plantation, which is what some, if not many, tree-planting initiatives probably turn out to be.
A lot of trees being planted are monocultures, which means they consist of many trees of the same species, and these species are usually fast-growing commercial species, like acacia or eucalyptus. In terms of biodiversity benefits, tree plantations do diddly-squat. Rich, natural forests are the way to go to boost and support biodiversity.
Source: Yale E360
Some tree plantations can also pose threats to water sources because trees are pretty thirsty organisms. According to a study on the impact of tree plantations, planting trees can dry up streams and change the soil quality in some areas. In fact, 13% of the forests studied caused streams to dry up for at least one year. And on average, plantations reduced stream flow in those ecosystems by 50%. Due to the water demands of tree plantations, natural wetland systems and aquatic habitats could be seriously disrupted. But these issues associated with the water and nutrient needs of trees also impact humans because obviously, we need water too! Tree plantations can limit the water available for drinking and irrigation. For example, in arid regions of China, planting trees is causing water scarcity.
So, next time you see a corporation committing to plant 2 million trees to account for their carbon emissions, ask yourself the following:
Where are these large scale tree-planting initiatives happening?
What purpose will they serve long-term i.e. are they planting a tree farm or a true forest?
Are they paying attention to what species they are planting i.e. native species?
Are they simply planting monocultures of tree species that are not diverse, which would be vulnerable to diseases and pests?
Clearly, there are a lot of local factors to consider when initiating a tree planting project. It is important to look at the big picture - whether the project will actually cause net cooling or warming - but then it’s equally important to scale it right down to the local level and make sure no harm is being done to the existing ecosystems and nearby communities.
Important Treeless Ecosystem
There are so many different types of ecosystems that thrive without trees and still combat climate change. Pleistocene Park in Siberia is an example of a region that thrives without trees. It is an Arctic, tundra ecosystem populated by musk-ox, wild horses, and bison. Nikita Zimov runs this park and his goal is to protect the frozen ground from thawing and thus emitting carbon. He said, “Here, trees worsen climate change,” and he’s right. This Arctic ecosystem relies on grazing animals to eat the ground vegetation and trample the snow to a thin layer. A thin layer of snow allows the ground to cool much more than a thicker, insulating layer would. However, when humans hunted most of the grazing animals from this area, the ecosystem began to transition from snowy grassland to forest, since the vegetation was not being eaten and could continue growing without limitation. An increase in trees has resulted in ecosystem warming. Nikita is one of many protectors of these vulnerable ecosystems and would like to see the Arctic rewilded and brought back to it’s natural, cool temperature.
Pleistocene Park in Siberia // Source: Animal People Forum
Prairies are also important ecosystems and they combat climate change on their own without a need for trees. Prairies reflect solar radiation and a study from the University of California found that in some areas, grasslands are even better carbon sinks than both tree plantations and natural forests because grasslands are more stable and reliable storers of carbon. Grasslands are less impacted by droughts and wildfires, so there is a lower risk of the carbon being emitted from these ecosystems. Plus, grasslands store carbon underground, so even if they were burned, the carbon would still safely be stored in the earth.
Many native grasslands have been destroyed by anthropogenic activities, such as agriculture and invasive species. We should start thinking about taking climate action by restoring these types of ecosystems instead of planting trees in areas that might not even be effective.
The American Prairie Reserve is an organization that is taking action to recover native prairie ecosystems. In Montana, they are working on removing non-native trees, like the Russian olive and Chinese locust, and reseeding abandoned cropland to restore the native prairie. Neil Shook, the manager of the projects, said, “I have old photos showing settlers out on the prairie, and there’s not a single tree in the background. Now the same places are littered with trees. By cutting trees we’re seeing increases in prairie vegetation and grassland songbirds.” So, this ecosystem is on its way back to thriving with native vegetation and wildlife and without trees.
Now, after all my researching and writing of this article, I still believe that planting trees is a way to combat the climate crisis. Trees, of course, are needed. Deforestation is still a huge, pressing issue for climate change. But the point to remember is that tree planting campaigns may not always be the answer to combating the climate crisis. We need to pay attention to planting trees in the right spaces, but we should also be sharing the spotlight with other types of ecosystem restoration - like grasslands and wetlands - that have their own critical ecosystem functions without the presence of trees. Maybe we will start to see carbon offsetting programs in the future that invest in other types of ecosystem restoration instead of simply planting loads of trees in places they may not belong.
Trees are complex, climate change is complex, and nature is complex. Being aware of the complexity of nature is important, so that we can support the right kinds of initiatives and have a better grasp on the role that trees have in climate change. It helps to do a little research, dig a little deeper, and keep on supporting helpful tree-planting efforts, while also diversifying your support by giving attention to other types of restoration projects. Trees are wonderful - personally, I love trees - but I think we should all start giving a little more love to those native grasses, shrubs, and other wildlife, and highlight the importance of those ecosystems as well.
The bottom line is that we as humans need to be very careful with how we rebuild nature. It is clear from history that many humans were not careful with nature in the past, which has led us to now - humanity facing a smorgasbord of issues that threaten our very existence. We know that nature is super complex, so obviously, restoring nature is going to be complex too. We need to tread lightly and be fully informed, and not cut any corners while doing so.
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