Satellite data shows that undisturbed forests will disappear completely in the large humid tropics by 2050 with current disturbance rates, new research shows.
Forests play a key role in stabilizing the environment; their carbon storage capacity offers a natural solution to climate change by controlling greenhouse gas emissions that warm the planet.
In a new analysis of patterns of deforestation and forest degradation caused by human activities over the past 30 years, scientists now estimate that nearly 219 million hectares or 17 percent of tropical rainforests have been lost. Of the remaining 1.07 billion hectares of tropical rainforests, 10 percent are degraded, usually an indicator that deforestation will follow, scientists said in a study published in Scientists progress.
“In more than 45% of cases, if measures had been taken to prevent degradation, deforestation – which occurred on average after 7.5 years – would have been avoided,” said Christelle Vancutsem, specialist in remote sensing and lead author of the study, who worked alongside a team of scientists from the European Commission Joint Research Center, the Center for International Forestry Research (CIFOR), the French Center for Agronomic Research for Development ( CIRAD) and the National Institute for Space Research (INPE) of Brazil.
To reach their conclusions, the researchers mapped land cover changes from 1990 to 2019 using Landsat imagery to observe how forest landscapes varied and changed over time, noting when they were undisturbed, degraded, pushed back, deforested, wooded or converted into plantations or water. Scientists also noted the dates and duration, recurrence and intensity of each disturbance.
Understanding disruption patterns can help countries meet the United Nations Sustainable Development Goals and their nationally determined contributions, which are a key component of reporting under the Paris Agreement strategy. United Nations to prevent post-industrial average temperatures from rising 1.5 degrees Celsius or more.
“It is now possible to monitor deforestation and degradation in tropical rainforests consistently over a long historical period and with fine spatial resolution,” said Vancutsem. “The mapping of the stages of the forest transition will make it possible to derive more targeted indicators to measure the achievements of the objectives of forest policy, biodiversity, health and climate. “
The results reveal the urgent need to strengthen actions to preserve tropical forests, in particular by avoiding the initial degradation which most likely leads to subsequent clearing of forests, she added.
Recognizing that no ecosystem can be considered truly undisturbed, scientists have defined forest degradation as canopy disturbance visible from space over a period of less than 2.5 years, resulting in loss of biodiversity. or carbon storage – or both.
Their research also shows that trends in deforestation rates appear to be linked to changes in national land policy, Vancutsem said. On the other hand, degradation rates are closely related to climatic conditions and are not affected by forest conservation policies. The situation seems to be accelerating, she added. “Over the five years from 2015 to 2019, we have seen a significant increase in forest degradation: 2.6 million additional hectares compared to the period 2010-2014.
This trend is explained by specific climatic conditions, in particular droughts and fires associated with the El Niño effect of 2015-2016. Deforestation and forest degradation are major threats to the climate and biodiversity.
“The conversion of forests for agricultural purposes is the second source of CO2 emissions into the atmosphere after the combustion of fossil fuels,” said Ghislain Vieilledent, co-author of the study and ecologist at CIRAD.
We understand from the results that it is of paramount importance to integrate measures that reduce degradation into forest conservation and climate change mitigation programs, Vancutsem added. They also show that forest degradation should be considered as a risk factor for deforestation and as an indicator of climate change and climatic oscillations.
“We hope that a better understanding of forest degradation processes and the resulting fragmentation will help to accurately assess the human impact on tropical ecosystem services and their impact on biosphere-atmosphere-hydrosphere feedbacks”, a- she declared. “Research indicates that future land management policies will need to take this finding into account. “
Data also shows that 41 percent of degraded pantropical forests are found in Asia-Oceania, nearly 40 percent in Latin America and just over 22 percent in Africa. 32 percent of deforested areas in tropical rainforests are in Asia-Oceania, 47 percent in Latin America and 21 percent in Africa.
Scientists have also learned that the distribution of secondary forests – defined as the regrowth of tree canopy after complete removal of tree canopy that has remained without tree regrowth for at least 2.5 years – is 46 percent in Asia – Oceania, 43 percent in Latin America and 11 percent. in Africa.
“We can confirm that most of the deforestation caused by the expansion of oil palm and rubber and attributed to the commodity classes in our study is concentrated in Asia,” said Vancutsem. “This equates to over 18 million hectares, which represents 86 percent of the total conversion of tropical rainforests to plantations, especially over 57 percent in Indonesia and over 23 percent in Malaysia. “
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