The giant fir trees in California can live up to 3,000 years, with a trunk diameter equal to the length of two cars, reaching over 90 meters. But a few years ago, in the midst of a record drought, scientists realized something strange. Some “giants” in Sequoia and Kings Canyon National Park are dying in an unprecedented way – from top to bottom.
When climbing up the canopy, the researchers found that the cedar beetle had chiseled some branches. By 2019, at least 38 trees have died – not a large number, “but worrying because they have never been observed,” said Christy Brigham, the park’s director of resource management.
Beetles have destroyed millions of pine trees across North America. However, scientists think that fir trees with anti-bug tannins will not hurt. They are investigating whether the combination of droughts and wildfires – which are increasingly exacerbated by climate change – have made it impossible for even sams to escape their invasion from dangerous bugs.
|The trees that can live to 3,000 years old now do not resist wildfires and insects.|
If so, these old trees would be the latest example of a trend being registered around the world. Trees in the forest are dying at a faster rate. Especially old and big trees.
According to a study in Science , this rejuvenates forests, threatens biodiversity, destroys important plants and animal habitats, and reduces the child’s ability to absorb CO2. people emitted from burning fossil fuels.
“We see this in almost every surveyed place,” said Nate McDowell, a scientist at the US Department of Energy, the lead researcher.
To paint a detailed picture of this situation, dozens of scientists around the globe have examined 160 previous studies, combined with satellite images. The results show that, from 1900 to 2015, the Earth lost more than one third of its old forests.
In the regions with the most detailed historical data – Canada, the western United States and Europe, the number of dead trees has doubled in just the past four decades, and perennials make up the majority.
There is no single direct cause. The researchers said that logging and deforestation for cropland were part of it. However, the increased temperatures and CO2 from burning fossil fuels have significantly strengthened the causes of plant death.
Severe and longer droughts, outbreaks of diseases, insects, and wildfires at the scale of disasters are increasing. These kill from eucalyptus and cypress in Israel, to birch and deciduous pine trees in Mongolia.
“We will see a decrease in the number of forests. Areas that are now forests in the future will disappear,” said Monica Turner, a forest ecologist at the University of Wisconsin.
|The forest is getting younger and younger.|
With more than 60,000 species of plants on Earth, this change occurs differently in each region.
In Central Europe, Mr. Henrik Hartmann (Max Planck Institute of Biochemistry, Germany) said: “You don’t have to look for dead trees. They are everywhere.”
Last year, after a week of prolonged heat, hundreds of thousands of oak trees had fallen their leaves. The beetle also destroys the sprout of plants – no wonder. However, hotter weather causes the tree to weaken, reducing the resistance of the tree, causing the bugs to multiply stronger and live through winter to the next year.
Even in cold regions, it only takes a few years hotter than usual for the forest to be damaged. “We are nearing a situation where the forest cannot adapt,” Hartmann added.
In 2019, huge wildfires broke out in Australia, 30,000 square kilometers of northern Siberia caught fire, and the Amazon suffered the same pattern.
In many parts of the Amazon, the dry season starts to last longer and arrives more often. Rainfall is only 1/4 and usually occurs as heavy rain, leading to flash floods (between 2009-2014). All this changes the balance of the trees in the forest. Species that grow faster and reach light faster, and are more resistant to drought, will overwhelm those that need moist soil to grow.
|Catastrophic forest fires are increasing.|
The consequences of these changes around the world are still being counted. The first study to evaluate the longevity of trees in Israel showed that many large patches of trees have disappeared, mainly due to heat and forest fires. In a country dominated by soil and sand, forests are of great importance. The tree is the nesting place for eagles, providing a habitat for wolves and jackals. The tree holds the soil with its roots. Without them, plants that live in the shade will face higher temperatures and more intense light.
Tamir Klein (Weizmann Institute of Science) states: “Big trees have a decisive role in the ecosystem for other plants and animals”.
In early June, Mr. Klein met with the Israel Forestry Bureau to discuss the southern forests of the country – they are expected to cease to exist by the end of the century. “They came and asked me what to do,” Klein said. They didn’t want the desert to expand. We’re facing a tough situation. A race to zero. “
Science’s research dates back to the early 2000s, when team leader McDowell moved to the northwestern United States to re-work at Los Alamos National Laboratory. Looking out the window, he saw that juniper and pine were dead. A heat wave caused 30% of the throughput on an area of 11,500 square kilometers. “Back then, I thought I would be here not long – as a plant physiologist, because they were all dead,” he recalls.
|The trees were pushed beyond their tolerance.|
McDowell and colleagues began to learn more broadly and deeply. Many people believe that increased CO2 levels will help plants grow faster. But when the Earth gets warmer, the atmosphere absorbs moisture from plants and animals. Plants will drop their leaves or close the breathing holes. Both reactions reduce the amount of CO2 they absorb. This is like “going to a buffet with a sticky tape” – Mr. McDowell said.
In a tropical forest, the major tree mass can lie in 1% – the largest trees in the forest. Study co-author – Craig D. Allen, a forest biologist – said: “These large old trees absorb large amounts of carbon on the ground. When they die, they leave space for smaller trees. But the amount of carbon absorbed is also greatly reduced. “
“When old plants die, they decompose, stop absorbing CO2 and start releasing this gas, like a broken thermostat. Global warming causes the plant to die, then the plant dies, making the situation worse. “.
|At the current rate, many forests will no longer exist in the future.|
While some changes in forests are hard to avoid, cutting emissions from burning fossil fuels can make a big difference. CO2 control over the next few decades could halve the area of destroyed forest in Grand Teton National Park in the future.
However, some other areas need more radical measures.
Mr. Klein suggested Israel consider planting acacia trees, which are common in the Sahara, to replace pine and cypress. This plant can grow even during the hottest days of the year.
“Sadly. They will look different. Everything will be different. But I think it is better than leaving the ground bare” – Mr. Klein added.