The world's most vital forests are dying twice as much as they did 35 years ago. Increasing tree deaths may be reducing the ability of many forests around the world to retain carbon by extracting greenhouse gases from the air. To properly understand what this means for carbon budgets, scientists must solve the conundrum of why trees are dying and how they respond to change. One of the main causes of death is climate change.
The frequent droughts of the past decade, largely related to rising temperatures, have not only created ideal conditions for fires, but have also weakened trees and made them more susceptible to insect infestation and disease. Forests around the world are transforming as the Earth warms and more frequent and severe droughts, wildfires and disease outbreaks destroy trees. It is well known that rising temperatures and increasing drought are causing the death of trees in forests around the world. She knew that fires are an integral part of forests in this part of the world; they prune smaller trees, give space to the rest, and even help the seeds of some species germinate.
Annual mortality rates are rising for Europe's major tree species, meaning forests will absorb less carbon and increase wildfire risks. Disagreements are often fierce, with opposing sides exchanging insults in the media and even holding competing forest summits. Not only are these deaths affecting larger trees, reducing forest carbon storage, but warmer, drier conditions are making it difficult for new trees to take root in the Rocky Mountains of southern Colorado, southern Wyoming, and northern New Mexico. But here in Colorado, researchers found that heat and drought alone are responsible for more than 70% of tree deaths in the 13 subalpine forest areas they measured over the past 37 years.
The studies are designed to broadly assess forest conditions on California's federal, state, and private lands. The seemingly aggressive goal, described in the journal Forest Ecology and Management, is based on the premise that this is the amount of vegetation that needs to be cleaned to give trees the space they need to grow strong and resistant. Broad implementation of new forestry techniques will require changes in government policy and acceptance from foresters and landowners. In a tropical forest, the vast majority of the tree mass can be in the top one percent of the largest trees.
Forests also absorb about a quarter of all human carbon emissions per year, and there are growing concerns that if forests become extinct, they will switch from storing carbon to emitting it, because dead trees will release all the carbon they have accumulated. The more diverse and naturally regenerating forest will also likely cope better with future droughts and pests, he says, because trees of different ages respond differently to such stresses, making it more likely that some will survive. But in Germany, as well as in the Czech Republic, Austria and elsewhere, foresters planted it in lower and much warmer regions. Widespread tree mortality and deforestation have disrupted the habitats of animals that are now critically endangered, such as the Sumatran tiger and the orangutan.
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