Observational evidence published in "Nature - Climate Change" Pronounced loss of Amazon rainforest resilience since the early 2000s indicates that the Amazon rainforest may be approaching the critical point of rainforest death - that is, the turning point from rainforest to savanna - from the 21st century So far, 75% of the region has lost its resilience.
01
In the context of climate change
The resilience of forests is decreasing
The internationally renowned academic journal "Nature" recently published an environmental research paper online that believes that as a response to climate change, the resilience of some forests is declining significantly. The authors of the
paper concluded that overall, as resilience continues to decline, it is estimated that about 23% of intact and undisturbed forests may have reached the critical threshold. Reduced forest resilience can have significant consequences for important ecosystem services of forests, such as carbon storage. Strategies for forest protection should take into account observed trends in forest resilience, they say.
In November 2018, California, USA, experienced the worst wildfire in history. The northern wildfire "Camp" burned over an area of more than 620 square kilometers, killing 85 people and leaving nearly 300 people missing. The area was then hit by heavy rains.
Wildfires are originally part of the natural process, but some studies have found that under the background of global climate change, the resilience of forest ecosystems is reduced after frequent wildfires.
Wildfires are originally part of the natural process. Appropriate wildfires will promote forest metabolism (such as the return of litter nutrients), and will also promote the survival and renewal of some species and the germination of some Pinaceae plant seeds. Therefore, due to its unique ecological benefits and functions, appropriate wildfires are beneficial, and the resulting ecosystem damage can be quickly restored.
Tree renewal ability is an important indicator of the recovery ability of forest ecosystems after wildfires. The success of tree regeneration mainly depends on the effects of temperature and drought stress on the seedling and sapling stages of trees. Some studies have found that the interactive effect of wildfires and drought climate after wildfires will reduce the regrowth ability of coniferous forests , which may slow down the recovery ability of the forest ecosystem, which will gradually lead the forest ecosystem to become more tolerant. Shrub and grassland ecosystems or shifts in dominant tree species.
Under the influence of global warming, drought and extreme weather, the interaction between increased wildfire activity and these factors has brought great uncertainty to the impact on the ecosystem. In recent years, some scientists have discovered that, in the context of climate change, the resilience of forest ecosystems is reduced after frequent wildfires. Stevens-Rumann et al. analyzed data from 52 wildfire events at 1,485 sampling sites in the Los Angeles Mountains of the United States in recent decades, and used the tree renewal ability after wildfires as a key indicator of forest recovery to explore the impact of wildfires on trees under climate change. Key factors in regeneration capacity, and mechanisms affecting tree regeneration failure.
This study found that compared with the 20th century, the regeneration capacity of trees after wildfires in the 21st century is significantly reduced, and adverse environmental conditions will prolong the regeneration of forest trees, or cause the forest type to shift to low-density forest or non-forest cover vegetation types. . During the time period studied, annual climate conditions trended toward warmer and drier conditions. Among them, compared with the period from 1985 to 1999, the lack of annual precipitation from 2000 to 2015 was very obvious, which was not conducive to the regrowth of trees after wildfires, thereby reducing the density of seedlings and the success rate of tree regeneration. Stevens-Rumann et al. also believe that changes in major climate factors have caused a reduction in the density and scope of forest ecosystems, which will have an important impact on the current and future forest ecosystem service functions.
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Climate change
is lowering the "ceiling" of forest carbon sequestration
In the context of climate change, many studies have found that forests are as fragile and sensitive as humans, which in turn weakens the potential of forests to sequester carbon; if not properly protected, forests can even It may turn from a valuable “carbon sink” into another source of greenhouse gas emissions.
Natural forests can better support biodiversity protection and achieve ecosystem services such as surface carbon storage, soil conservation, and water source conservation. In the context of climate change, forests are as fragile and sensitive as humans. If not properly protected, it may accelerate the climate crisis. Take the Amazon rainforest as an example. Years of fires and tree death have gradually turned this "magic" forest into a "carbon source" that emits net carbon dioxide.
At present, "forest restoration" has been placed high hopes by the international community as an important "nature-based solution", that is, increasing the forest area to absorb and store carbon dioxide to cope with global climate change.
Research has found that natural forests are more valuable than artificial forests in terms of the three ecological goals of protecting biodiversity, surface carbon storage, soil conservation, and water conservation; however, artificial forests are significantly more effective in wood production functions. in natural forests. Therefore, the efficient use of plantations to achieve timber production goals can reduce the clearing of natural forests with higher ecological benefits, thereby indirectly providing ecological benefits. The research team also found that there are many old or abandoned plantations around the world that are no longer used for timber production. Restoring them into natural forests can more economically bring ecological dividends.
The long-term carbon sequestration capacity of a forest depends on its ability to preserve carbon in the form of biomass. In scientific research, surface biomass is often used to measure the level of forest carbon storage. And various natural disturbances, such as hurricanes, fires and droughts, can reduce the long-term carbon sequestration capacity of forests. Global climate change has intensified the erosion of forests by this natural disturbance. At the same time, the "fragmentation" of forests has also caused forest degradation, further reducing the carbon sequestration capacity of forests.
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The forest climate tipping point will be reached in 2050
The research team of Kathalyn Duffy of Northern Arizona University in the United States analyzed the carbon dioxide trajectory records between the ecosystem and the atmosphere of the Global Observation Network (FLUXNET) from 1991 to 2015 and found that Under current trends in greenhouse gas emissions, ecosystems that store the most carbon dioxide (such as tropical rainforests and temperate forests) may lose more than 45% of their carbon storage capacity by the middle of this century (around 2050). By the end of this century, half of the plants in Earth's terrestrial ecosystems may be releasing carbon into the atmosphere faster than they can absorb it!
A study by the University of Exeter in the UK has found that the resilience of the Amazon rainforest is waning. Once a tipping point is exceeded, forests may be replaced by grasslands. But experts point out that this "tipping point" is not inevitable and call for an immediate halt to deforestation of tropical rainforests.
According to the " New York Times " report on March 7, since 2000, the Amazon rainforest has experienced an increase in droughts, and it takes longer and longer to recover. One of the researchers, Tim Renton, director of the Global Systems Institute at the University of Exeter, warned that losing the Amazon rainforest could result in nearly 90 billion tonnes of carbon dioxide - equivalent to several years of global emissions - returning to the atmosphere, or Will intensify global warming in . The replacement of tropical rainforests by savannas will also greatly reduce the habitats of different species.
The study did not determine when the so-called "tipping point" will be reached. However, it can be predicted that by the end of the 21st century, deforestation, climate dryness and other factors may cause the Amazon's tropical rain forests to shrink significantly.
More than three-quarters of untouched rainforests have "lost their elasticity", with the situation most severe in areas that are drier or have more deforestation, the study found. Chris Bolton, the lead author of the study and a researcher at the University of Exeter, pointed out that the Amazon is like a huge water circulation system. The shrinking of the rainforest will make the area drier, which in turn will accelerate the resilience of the ecosystem. exhaustion.
Paul Brando, a tropical ecologist at the University of California, Irvine, believes a "tipping point" is not inevitable and calls for an end to tree clearing in the Amazon. He pointed out that the rainforest ecosystem is highly elastic, and reduced elasticity does not mean its complete loss. If it is not damaged over time, it is still expected to recover quickly.
Carlos Nobre, a senior scientist at Brazil’s National Amazon Research Institute, was one of the first scholars to call attention to the protection of the Amazon rainforest more than 30 years ago. Although he was not involved in this study, he said that the latest research results are very worthy of attention. "We have to achieve zero deforestation, zero forest degradation, and we still have a chance to save the Amazon rainforest," Nobre said.
The Amazon tropical rainforest is the world's largest tropical rainforest with the most species. It is known as the "Lungs of the Earth" and plays an important role in absorbing carbon dioxide, slowing down climate change, and protecting biodiversity. About 17% of tropical rainforests have been cleared over the past half century, and although the rate of deforestation slowed for a few years, it has picked up in recent years. As one of the wettest regions in the world, the Amazon has experienced drought three times since 2000.
Forest is the ecosystem with the largest distribution area, the most complex structure and the richest biodiversity on land. It is known as the master regulator of nature and the "lungs of the earth", maintaining the global ecological balance. Forests have many ecological functions such as conserving water sources, preserving soil and water, preventing wind and sand, resisting disasters, vacuuming and sterilizing, purifying air, regulating temperature, improving climate, protecting species, preserving genes, fixing carbon and releasing oxygen, etc. They are important for maintaining the ecological security of the earth. Assure. Scientists assert that if forests disappear from the earth, more than 90% of the world's living creatures will become extinct, and humans will not be able to survive for a year.
Forests are the habitat of more than 3/4 of the world's
terrestrial organisms.
absorb about 2 billion tons of carbon dioxide every year
and provide large amounts of drinking water for more than 1/3 of the world's big cities.
It is very important to us.
It is called " "Lungs of the Earth"
However,
a cigarette butt
can burn tens of thousands of acres of green to ashes
a single negligence
can make the forest disappear in an instant
According to statistics
more than 97% of our country's forest grassland fires are caused by humans
Protect the forest , is to treat ourselves well
Source: Ecological China Network comprehensively compiled
