Climate crisis: what can trees really do for us? Experts say that trees over 100 years old have seen a drastic change in the level of carbon dioxide in the atmosphere. That number changes dramatically from 280ppm 175 years ago to 415ppm today, yet it continues to grow rapidly.
Measuring how these trees are affected, including their growth, weight and chemical composition, can help us understand their role in mitigating climate change (climate crisis). Thanks to the power of sunlight, forests turn huge amounts of carbon in the air into food: sugars for themselves, leaves, bark, and roots that feed on animals and microbes.
Respiration, which occurs in the cells of all living things in the wild, releases energy and carbon dioxide (CO₂) from that food into the air. As the amount of carbon in the atmosphere increases, this food and drink cycle continues. Metabolically speaking, trees walk to stand still. During this cycle, forests approach a significant portion of the 33% of human-caused emissions removed from the atmosphere each year.
I (Rob) work in a forest full of beautiful 175-year-old oaks. Global carbon dioxide levels were about 280 parts per million (ppm) when these trees were planted. The global atmospheric concentration has now exceeded 415 parts per million and is increasing rapidly.
If these oaks reached 200 years old (not the age of the oak), they would be surrounded by air containing about 550 parts per million of carbon dioxide. Can the world’s mature forests withstand these changing conditions and continue to offset some of our emissions from burning fossil fuels?
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To find out, my colleagues and I at the University of Birmingham’s Forest Research Institute use a free-air carbon dioxide enrichment facility. Imagine a dinosaur-free Jurassic park 102.25 meters high, treating patches of forest with carbon dioxide-rich air that simulates a mid-century atmosphere: 565 ppm 150 ppm above current levels.
Then we measure everything we can: the width of the tree trunk, the size, weight and chemical composition of the leaves, the branching geometry of the roots and more. In this way, we record changes in the creation and health of forest commodities.
climate change crisis real impact
Our first results are in the foreground. In the canopy, the rate of photosynthesis is a third higher than on sunny days in carbon dioxide-rich spots. In the growing season, the increase is about a fifth. Those are big numbers: imagine your annual income increased by a fifth. Photosynthesis is the carbon input into the forest.
Since we began this experiment in 2017, patches of forests exposed to rising carbon dioxide appear healthy and productive. This may seem surprising. After all, plants love carbon dioxide so much that farmers add it to greenhouses to increase the growth of fruits and vegetables.
But the forests are not cared for. They must fend for themselves, winning (along with their innate partners) all the nutrients they need to balance any carbon dioxide wealth from the ground they are standing on. An excess of carbon dioxide in sugar can be very good for photosynthesis, as can an imbalance in our diet.
Climate change crisis
Think of forests as running carbon accounts, bringing in carbon through photosynthesis and spending it on respiration, giving all the energy that keeps everything alive in the forest. In a healthy and productive forest, at the end of each year a little more comes out than goes out of the current account.
Forest carbon current accounts can hold carbon in their perennial woods, roots and soils for decades, sometimes centuries, linking us to a 21st century peak in atmospheric carbon dioxide, a carbon cash-flow crisis fueled by fossil fuels and forests.
Well-managed forests can produce wood and fuel while reducing carbon in the atmosphere. But carbon savings accounts are also needed, which keep things away for thousands of years by pumping them into deep underground reservoirs, for example.
People and trees
Scientific models have estimated how much tree planting or reforestation is needed to offset the rise in carbon dioxide in the atmosphere. As with most attempts to translate theory into action, the real world experiences of actually doing this are often really messy. How to fund deforestation campaigns and encourage farms will determine where and what types of trees are planted.
Ultimately, how the land is governed will also determine how long the new trees will live. International efforts to develop the planet’s tree cover show how difficult it is to overcome these obstacles. A recent study in northern India found that decades of costly tree planting programs did not increase total canopy cover. The cultivated areas did not bring any significant benefits to the local population, such as new food or firewood.
Carbon & Trees
This was because new trees could not be planted on a neighboring farm, and so were added to areas with few trees already, reducing the potential carbon savings for the entire effort. The local forest dwellers were also preoccupied with achieving tree-planting goals rather than nurturing the types of forests and trees valued by the locals.
Earth is not just carbon & Trees and forests make up the microclimate and water cycle, support biodiversity and provide food, building materials, and medicine for the local population. They also have different cultural and spiritual values depending on where you are in the world. Forests often lie within landscapes that are occupied by farms and all kinds of other uses, such as towns and cities.
Everyone has different preferences about what a scene should look like, and who their vision wins depends on the power relationship. In 2014, researchers working in Uganda described what they called carbon colonization: farms erected to offset greenhouse gas emissions destroyed local people’s crops and burial sites, blaming those who were previously public and accused of trespassing on the land.
This is one of the many examples of tree planting, regardless of good intentions, living a hopeless life. Using trees as a tool becomes unfair when it involves asking poor rural people to bargain over their livelihoods so that the rich or nations can continue to consume fossil fuels. Instead of asking if trees can help tackle the climate crisis, perhaps we should ask how much the world really depends on trees as a climate solution.
Benefits to local people
Much can be learned from efforts that have been successful in increasing tree cover and providing benefits to local people, such as new sources of income. These initiatives are often successful because they take local needs and values seriously. The local and indigenous people are the leaders in the process, not the ideas. Finally, deforestation will be successful if it benefits people as well as the planet.