For more than a decade, Brazil has been aggressively fighting deforestation in the Amazon, including through a legal mandate in the Forest Code that landowners in the region maintain as much as 80% of their forest cover. Yet selective logging and road-building are still permitted. Forest fires are also common, mostly started by burns on nearby agricultural fields.

As forest degradation due to human activities has become more visible, scientists have begun to try to gauge the impact. A new study published in the journal Nature for the first time quantifies the collective impacts of all these disturbances on forests in the Brazilian state of Pará, comparing them with losses from deforestation.

A giant Amazonian carrion scarab beetle. Photo by Hannah Griffiths. Click to enlarge.The international study team, which included researchers from 18 institutions, assessed the occurrence of 1,538 plant, 460 bird and 156 dung beetle species throughout Pará – an area the size of South Africa that has been a focal point of Amazon protection efforts. They found that even in landscapes that have the highest level of protection under Brazil´s Forest Code, disturbed forests had lost 46–61% of their conservation value.

“We provide compelling evidence that rainforest conservation initiatives must address forest disturbance as well as deforestation,” said Jos Barlow, lead author of the study and a professor of conservation science at Lancaster University in the UK. “Without urgent action, the expansion of logging operations and the spread of wildfires fuelled by human-induced climate change mean that tropical forests are likely to become increasingly degraded, conserving only a fraction of the breathtaking diversity they once harboured.”

Selective logging in the Jari region, in northern Pará. Photo by Jos Barlow. Click to enlarge. For context, the impacts of disturbance across Pará have resulted in a loss of biodiversity equivalent to clearing 92,000–139,000 km2 of primary forest. This is greater than the area deforested across the entire Brazilian Amazon between 2006 and 2015. The implications are significant, as not only are tropical forests a unique storehouse of species found nowhere else on Earth, but they are also a vital element of the Earth’s biosphere, helping sustain the climate and hydrological systems on which millions of livelihoods depend.

“The functional impairment of forests at such large scales means we cannot depend on them to provide the same level of ecosystem service anymore,” said co-author Toby Gardner, a senior research fellow at SEI in Stockholm. “These results should serve as a wake-up call to the global community. Brazil demonstrated unprecedented leadership in curbing deforestation in the last decade. The same level of leadership is now needed to protect the health of the forests that remain in Brazil and across the tropics. Otherwise, decades of conservation effort will have been in vain.”

Rare species are the most affected

The scientists also found that the species under the greatest threat of extinction suffered most from human disturbances. Dr. Alexander Lees of Cornell University, the project’s lead ornithologist, explained: “The state of Pará is home to over 10% of Earth’s bird species, many of which are unique to the region. Our results show that it is these endemic species that are suffering most from the effects of human disturbances, because they cannot survive in disturbed forests.”

Lead project analyst Dr. Gareth Lennox of Lancaster University added: “Tropical forests are one of Earth’s most precious biological treasures. By focusing on the extent of forests that remain and ignoring their health, current national and international conservation strategies are inadvertently placing that treasure in jeopardy.”

Going beyond tackling deforestation

Indeed, although reducing deforestation is rightly the cornerstone of most conservation strategies in tropical nations, the condition of the remaining forest is rarely measured, let alone controlled by policy initiatives.

“Immediate action is required to combat forest disturbance in tropical nations,” explained Silvio Ferraz from the University of São Paulo. “This is particularly important in Brazil, which holds up to 40% of the world’s remaining tropical forests.”

Unfortunately, Brazil’s unique biodiversity is once more imperiled by continued attempts to undermine its environmental legislation. Dr. Joice Ferreira of the Brazilian Agricultural Research Institute in the Amazon, who co-led the study, offered an example: “Our Senate is proposing a new law that would allow producers to use tree plantations, such as eucalyptus monocultures, to meet their legal requirements for forest cover. Proposals such as these, that fail to consider forest condition, would further accelerate the loss of tropical biodiversity.”

Read the article (external link to journal)