Pollution, droughts, heat waves, and pests are killing many of our trees. Climate change is involved in all these causes. In addition, climate change feedback loops are accelerating the extinction of trees.
Feedback loops accelerate global warming. For example, global warming has resulted in tree deaths and deforestation. Trees are a natural carbon sink for carbon dioxide, as well as, provide shade, retain moisture, and aid in cooling. As trees die from the effects of global warming, climate change is accelerated resulting in more tree deaths. Scientists' warning to humanity on tree extinctions, "This evidence suggests that a third of the world's tree species are currently threatened with extinction, which represents a major ecological crisis. Large-scale extinction of tree species will lead to major biodiversity losses in other species groups and substantially alter the cycling of carbon, water and nutrients in the world's ecosystems. Loss of tree diversity could lead to abrupt declines in ecosystem functions and services, and ultimately ecosystem collapse."
Wildfires also are a climate change feedback loop. As the planet warms, wildfires increase. Wildfires destroy the carbon sink of forests, and spew massive amounts of greenhouse gas emissions into the atmosphere. The result is an increase in global warming. The increase in global warming results in more wildfires resulting in desertification.
In 2020, 20% of all the forests in Australia burned. Some of these forests hadn't seen fires in the last 35,000 years. "More than 24 million hectares (59 million acres) burned during Australia's devastating 'Black Summer' bushfire season of 2019-2020, which formed part of a confirmed climate change-driven trend of worsening fire weather and larger, more intense forest fires," reported Mongabay News.
The 2021 fire season saw a record number of acres burned in the Northwestern USA and Canada. In California a total of 8,835 fires were recorded, burning 2,568,948 acres (1,039,616 ha) across the state. Over 1.4 million acres burned in Oregon and Washington. "Three times in the past five years, over 10 million acres have burned nationwide. On average, over 2 million more acres burned each year in the 2010s than during the 1990s," reports Spokane's KXLY.
Research published in the Proceedings of the National Academy of Sciences reports, "by 2070, around 2 billion people are expected to live in extremely hot areas" similar to the Sahara Desert.