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Climate change creates an unclear future for U.S. forests

Forests play an important role in mitigating climate change. They absorb carbon from the atmosphere through photosynthesis, storing it in their trunks, branches, leaves, and roots. This carbon storage superpower is one of the reasons why forests have been identified as a potential climate solution, in addition to reducing human greenhouse gas emissions. 

However, a recent study published in the journal Nature Geoscience suggests that climate change itself might compromise how permanently forests are able to store carbon and keep it out of the air.

The study was conducted by Zhaosheng Wu, a postdoctoral researcher at Stanford University’s School of Earth, Energy & Environmental Sciences, and William Anderegg, an assistant professor at the University of Utah‘s School of Biological Sciences.

The researchers looked at how different regions and tree species in the United States would respond to climate change and found a wide range of estimates of how much carbon forests in different regions might gain or lose as the climate warms. They also found that the regions most at risk of losing forest carbon through fire, climate stress, or insect damage are those where many forest carbon offset projects have been set up.

“This tells us there’s a really urgent need to update these carbon offsets protocols and policies with the best available science of climate risks to U.S. forests,” said Anderegg.

For this study, the researchers were interested in forecasting changes in the amount of aboveground carbon storage in forests of different regions in the United States. Aboveground carbon refers to any living parts of a tree that are above ground, including wood and leaves or needles. 

To do this, the experts used a combination of methods, including historical and future projections of climate, datasets from long-term forest plots, machine learning, and complex models that include interactions between the ecosystem and the atmosphere.

“Each different method has inherent advantages and limitations,” said Wu. “No model is perfect.”

“By bringing in many different approaches and different model types and comparing them, we can get a sense of what the different models are telling us and how can we learn to improve the models. And we might have much more confidence if all of the models and all of the approaches tell us the same story in a given region,” said Anderegg.

Despite the differences in the models’ forecasts, the researchers found some consistency in predictions of how different regions’ carbon storage might change in the future. For example, the Great Lakes and Northeastern US, as well as parts of the Southeastern US and the northern Rockies, consistently showed carbon gains in future projections. However, the models also showed significant risks of losing carbon from forests through the climate triple threat of fire, climate stress, and insect damage.

With those risks, the models projected a net carbon gain in forests nationwide of between three and five petagrams of carbon by the end of the 21st century (a petagram is a quadrillion grams – about 25 times the mass of all humans on Earth). Without those climate stresses, forests might be able to pack away a net 9.4 petagrams of carbon.

The researchers also applied their analysis to 139 current projects to offset carbon emissions to the atmosphere by aiming to increase the carbon stored in forests through various approaches. However, depending on the model method and the climate scenario, the results showed that large numbers of carbon offset forest projects, particularly in the Southeastern US and on the West Coast, are projected to lose carbon by the end of the century.

“For carbon offsets to be effective, they have to store carbon for a pretty long amount of time – multiple decades to centuries. So if fire’s burning them down or insects are wiping out different areas, it could vastly undermine their effectiveness as climate change solutions,” explained Anderegg.

The experts found that tree demographic models, which simulate forest dynamics by tracking the growth of new trees and the death of old ones, do not account for the potential influence of different types of vegetation that appear following a disturbance like a forest fire. 

Additionally, these models do not consider the potential for rising carbon dioxide levels to improve plant growth, a phenomenon known as CO2 fertilization.

“These current models didn’t consider the disturbance-vegetation feedback,” said Wu. “And also they didn’t consider CO2 fertilization.”

Ultimately, Wu and Anderegg identified three key areas of research that could improve climate projections. First, they suggested investigating how rising concentrations of carbon dioxide may benefit plant and tree growth. 

Second, they identified the need for better data and understanding of climate-driven tree mortality caused by factors such as fire, climate stress, and insects. 

Finally, they highlighted the need to investigate how biomes will shift around following a disturbance, such as how some forests may be able to grow back while others may transition to grasslands and be lost entirely.

“These are some of the biggest unknowns that the field is really racing to tackle,” said Anderegg. “Working to tackle climate change as quickly as possible and move to a lower carbon future massively decreases the risks that forests are likely to face in the 21st century and increases the potential benefits that we might get from forests.”

The study highlights the importance of further research to improve our understanding of the complex interactions between climate change, forests, and the wider environment. By doing so, we can better prepare for the challenges that lie ahead and work towards a more sustainable future.

Why forests are so important

Forests are one of the most important ecosystems on Earth, and they provide a wide range of benefits to both humans and the environment. From regulating the climate to providing habitat for millions of species, forests play a critical role in the health and well-being of the planet.

It is important to understand the complex interconnections between forests and other ecosystems, as well as the ways in which human activities can impact these systems. In this article, we will explore the many reasons why forests are so important to Earth’s ecosystems, and why we must work to protect and conserve them for future generations.

Regulating the Climate

Forests play a crucial role in regulating the Earth’s climate, acting as carbon sinks that absorb large amounts of carbon dioxide from the atmosphere. Trees absorb carbon dioxide through the process of photosynthesis, which converts carbon dioxide and sunlight into energy and oxygen. This process helps to reduce the amount of carbon dioxide in the atmosphere, which in turn helps to mitigate the effects of climate change.

Additionally, forests help to regulate local and regional climates by controlling temperature and humidity levels. The canopy of trees provides shade and helps to cool the air, while the soil and vegetation help to retain moisture and prevent flooding.

Biodiversity and Habitat

Forests are home to millions of species of plants and animals, and they provide critical habitat for many endangered and threatened species. The dense canopy of trees provides cover and nesting sites for birds, while the forest floor provides a habitat for small mammals, reptiles, and amphibians.

Forests are also home to a wide range of plant species, many of which are used in traditional medicine and as a source of food and shelter for wildlife. The loss of forests can have a devastating impact on biodiversity, as species lose their habitat and are forced to compete for resources in an increasingly degraded environment.

Soil Conservation

Forests play a critical role in soil conservation, helping to prevent erosion and maintain soil health. The root systems of trees help to stabilize the soil, preventing erosion and landslides, while the leaves and other organic matter provide nutrients and promote soil fertility.

Forests also help to maintain water quality, acting as natural filtration systems that remove pollutants and other contaminants from water sources. The loss of forests can lead to increased soil erosion, water pollution, and other environmental problems.

Economic Benefits

Forests provide a wide range of economic benefits, from timber and other forest products to ecotourism and recreational opportunities. In many parts of the world, forests are a vital source of income for local communities, providing jobs and supporting local economies.

However, the economic benefits of forests must be balanced with the need to protect and conserve these vital ecosystems. Sustainable forestry practices, such as selective logging and reforestation, can help to ensure that forests continue to provide economic benefits without sacrificing their ecological value.

In conclusion, forests are one of the most important ecosystems on Earth, providing critical services to both humans and the environment. From regulating the climate to providing habitat for millions of species, forests play a vital role in maintaining the health and well-being of the planet.

As humans, it is our responsibility to study and understand the complex interconnections between forests and other ecosystems, and to work to develop sustainable solutions to the many environmental challenges we face. By working to protect and conserve our forests, we can help to ensure a healthy and sustainable future for generations to come.


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