Climate Change: West vs. East – How Forests Respond

Climate change is having a profound impact on forests across the United States, but new research shows that the effects are not uniform. A recent analysis of U.S. Forest Service data reveals a pronounced regional imbalance in forest productivity, with the consequences of climate change hitting the American West particularly hard. Led by UF Biology researchers J. Aaron Hogan and Jeremy W. Lichstein, the study warns that rising temperatures, escalating droughts, wildfires, and disease outbreaks are taking a toll on trees and reshaping forests in different ways.

Forests play a critical role in regulating the Earth’s climate by acting as carbon sinks, sequestering approximately 25% of human carbon emissions annually. However, this ability to store carbon relies on a delicate balance between the positive and negative effects of climate change. As the study using national-scale forest inventory data shows, the Western U.S. is experiencing a notable slowdown in forest productivity, while the Eastern U.S. is seeing slightly accelerated growth. This disparity indicates that the impact of climate change is not uniform and varies depending on the region.

Drivers of Change: Carbon Dioxide Fertilization and Climate Change

Some drivers of climate change, such as droughts and forest pathogens, have negative effects on forest productivity. However, other drivers, such as carbon dioxide fertilization, are predicted to have positive effects. This phenomenon suggests that increased carbon dioxide levels enhance plant growth by increasing photosynthesis. To investigate this further, the researchers analyzed data from the U.S. Forest Service, which has been monitoring tree growth and survival across the country for decades.

The Reality of Forest Growth in a Changing Climate

While tree growth in the Eastern U.S. aligns with expectations, the Western region tells a different story. Extreme climate effects overshadow any potential positive growth trends, challenging the prevailing assumption that forests’ carbon-storing ability will continue to increase. This finding carries significant implications for future climate and sea-level rise projections, as ecosystems are likely to store less carbon in the future, leading to more carbon in the atmosphere and accelerating climate change.

Climate Change as a Dynamic and Region-Specific Agent

This study highlights the fact that climate change is not a uniform force but rather a dynamic agent with region-specific influences. The degree of climate change can push forests past a tipping point, leading to irreversible damage. Some forests are already approaching or surpassing climate thresholds, which shift them from being carbon sinks to becoming carbon sources. The Western U.S. is already experiencing this reversal of carbon sequestration, and there are concerning signs that other drought-impacted regions, such as the Amazon, may be following suit.

Contrary to popular belief, the decline in productivity in the Western U.S. cannot solely be attributed to increased rates of tree mortality caused by wildfires. The study reveals that declining tree growth rates are a significant factor contributing to the additional loss of ecosystem carbon in Western forests. With adverse climate change effects, including decreased precipitation, trees are growing slower, causing the carbon sink in Western forests to weaken. Urgent action to reduce human greenhouse gas emissions is necessary to mitigate these effects and restore the health of these forests.

This research raises concerns about the future resilience and sustainability of U.S. forests. The findings underscore the urgent need for governments and industries to work together to reduce greenhouse gas emissions and achieve net-zero emissions as soon as possible. The scientists stress that reduced global greenhouse gas emissions are crucial to prevent further weakening of forest carbon sinks, as this would only accelerate the pace of climate change. It is imperative to recognize the vital role that healthy forests play in connection with emissions reduction to restore the global carbon balance.

Climate change is reshaping forests across the United States, but the effects are not uniform. The Western U.S. is experiencing a significant slowdown in forest productivity, while the Eastern U.S. shows slightly accelerated growth. Forests’ ability to store carbon hinges on the delicate balance between the positive and negative effects of climate change. The study underscores the urgent need to reduce greenhouse gas emissions and highlights the region-specific influences of climate change. To ensure the resilience and sustainability of forests, immediate action is necessary to mitigate the consequences of climate change and protect these invaluable ecosystems.