Amazon landscape change study highlights ecological damage and opportunities for action – Eurasia Review


A major study of landscape change in the Brazilian Amazon sheds new light on the many environmental threats facing the biome – but also offers encouraging opportunities for ecological sustainability in the world’s most biodiverse rainforest.

The findings of the study are critical because, as the Amazon moves closer to a “tipping point,” they provide a solid foundation to inform priorities for conservation and regeneration that are urgently needed in the forest. . They show that gains can be achieved through a series of actions – including, but not limited to, stopping deforestation.

The research, which is published today in the scientific journal ‘Proceedings of the National Academy of Sciences‘ (PNAS), was conducted by an international team of scientists from Brazil and the United Kingdom. They examined the ecological impacts caused by the changes people are making to forest landscapes in two regions of the Brazilian state of Pará – Santarém and Paragominas.

“While the focus so far has been on deforestation, we know that tropical forest landscapes are altered by a much wider range of human activities,” said lead researcher Dr Cássio Alencar Nunes. from Universidade Federal de Lavras in Brazil and Lancaster University in the UK. . “These changes include deforestation and degradation of primary forest, for example through selective logging and fires, but even deforested landscapes change as agricultural abandonment causes secondary forest to re-grow. As a result, many Tropical landscapes are now a mosaic of non-forest land uses, regenerating secondary forests and degraded primary forests.

By studying the rate of transformation between different land uses and their impacts on ecological status, researchers have identified transitions that are common and have high ecological impacts, as well as those that have large impacts but occur less frequently.

“Our results revealed a better understanding of how people affect the Amazon and its ecosystem,” said Dr Alencar Nunes.

Collecting data from 310 plots, the researchers studied how changes affect biodiversity, examining more than 2,000 species of trees, vines, birds and insects. They also looked at the properties of carbon and soil.

The researchers also used published data from 2006 to 2019 on how quickly the landscape has changed over the past decade.

Their results show that transitions from primary and secondary forests to pastures through deforestation amount to 24,000 km² per year. They found that the species richness of almost all biodiversity groups decreased by 18-100% on plots where primary or secondary forest had been converted to pasture or mechanized agriculture. Transitions from forest to mechanized agriculture had the greatest ecological impact but occurred less frequently than conversion of forest to pasture.

“Deforestation of primary forests to create pasture is the most damaging land use change in the Brazilian Amazon,” said Dr Alencar Nunes. “Our results show that transitions from primary forest to grassland have always been classified as ‘high impact, high rate’ for biodiversity, carbon storage and soil properties. This highlights the critical and urgent importance of tackling deforestation, which has increased in recent years.

However, the study also revealed opportunities for positive action, for example highlighting the importance of protecting secondary forests and allowing them to mature. They found that the diversity of large trees doubled and the diversity of small trees increased by 55% when young secondary forests became over 20 years old, leading to gains in biodiversity and carbon storage.

Other results revealed less obvious forms of degradation that affect the ecology of the Amazon. They found that switching from one type of agriculture to another, from cattle grazing to more intensive mechanized agriculture, also decreases biodiversity, with the diversity of ants and birds decreasing by 30% and 59% respectively. .

Dr Alencar Nunes said: “These are important findings because they show that there are a multitude of actions that can be taken to protect and improve the ecology of the Amazon. When farmers replace pasture with cropland using mechanized farming methods, this also impacts biodiversity, but it is a process that is largely hidden from deforestation.

“By reducing the amount of land converted to mechanical agriculture and allowing secondary forests to regrow, we can achieve significant ecological restoration gains in the Amazon.

“Our analysis helps define and prioritize the local and regional actions needed to stimulate a better Amazon.”

Co-author Jos Barlow, professor of conservation science at the Lancaster Environment Center at Lancaster University, pointed out that the study has further implications for conservation and policy.

He said: “Our results again underscore the importance of addressing deforestation, as well as the additional benefits of avoiding degradation and improving the permanence of secondary forests. However, achieving this will require transforming the way the Amazon is currently managed, including much better integration of local science, policy and practice.

“We also highlight the need to focus on biodiversity as well as carbon in tropical forests – of the three ecosystem components we analyzed, biodiversity was the most affected by all land use changes. We hope that biodiversity can be included in climate change mitigation actions, and that this will be highlighted at the upcoming COP15 on biodiversity.


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