̽��ֱ�� of Cambridge - Toby Gardner

Amazon deforestation ‘threshold’ causes species loss to accelerate

fpjl2 — Wed, 04 Mar 2015 13:51:28 +0000

One of the first studies to map the impact of deforestation on biodiversity across entire regions of the Amazon has found a clear ‘threshold’ for forest cover below which species loss becomes more rapid and widespread.

By measuring the loss of a core tranche of dominant species of large and medium-sized mammals and birds, and using the results as a bellwether, the researchers found that for every 10% of forest loss, one to two major species are wiped out.

This is until the threshold of 43% of forest cover is reached, beyond which the rate of biodiversity loss jumps from between two to up to eight major species gone per 10% of disappeared forest.

While current Brazilian law requires individual landowners in the Amazon to retain 80% forest cover, this is rarely achieved or enforced. Researchers say that the focus should be shifted to maintaining 50% cover – just half the forest – but over entire landscapes rather than individual farms, in a bid to stop whole regions losing untold biodiversity by slipping below the 43% threshold at which species loss accelerates.

Unless urgent action is taken to stem deforestation in key areas that are heading towards or have just dipped below the forest cover ‘threshold’ – which, according to the research team’s models, amounts to a third of the Amazon – these areas will suffer the loss of between 31-44% of species by just 2030.

“These results support the need for a major shift in the scale at which environmental legislation is applied in Brazil and the tropics,” said Dr Jose Manuel Ochoa-Quintero, from Cambridge ̽��ֱ��’s Department of Zoology, who led the study, published recently in the journal Conservation Biology.

“We need to move from thinking in terms of compliance at a farm scale to compliance at a landscape scale if we are to save as many species as we can from extinction."

̽��ֱ��researchers worked across an area of the North West Amazon over three million hectares in size. They then divided the region into 1,223 squares of 10,000km, and selected 31 squares representative of the spectrum of forest cover across the region (12-90% cover). 27 squares consisted of private land; only four were protected areas (PAs). PAs were only areas in region with almost complete forest cover.

Within the 31 squares, researchers analysed the presence of 35 key species of mammals and birds for which these regions are natural habitats, such as pumas, giant anteaters and red howler monkeys. This was done through a combination of direct observation and recording evidence such as footprints and faeces, as well as in-depth interviews with landowners and residents, who were quizzed about species presence through photographs, animal noises and local knowledge.

̽��ֱ��researchers found a cut-off, conservatively given as 43% forest cover, below which the squares held “markedly fewer species”, with up to eight key species lost for every 10% of further deforestation beyond this threshold.

“This is not just a result of overall loss of habitat, but also reduced connectivity between remaining forest fragments, causing species to hunt and mate in ever-decreasing circles,” said Ochoa-Quintero. “This fragmentation may be the key element of the ‘threshold’ tipping point for biodiversity.”

Encroaching agriculture – from beef to soya production – to feed a growing and more affluent human population means that, at the current rates, the number of 10,000km2 landscapes in the Amazon that fall below the species loss threshold of 43% forest cover will almost double by just 2030. At current rates, by 2030 only a mere 22% of landscapes in the region will be able to sustain three quarters of the key species surveyed for the study.

̽��ֱ��expansion of agriculture in recent decades means that around 41% of the original forest in the study region – some two million hectares – has been lost over just the last 40 years.

Researchers say that while PAs can counter agricultural expansion – and many have increasingly called for PAs to expand across the planet amid dire evidence of rapid species decline – the limits on land that can be set aside for PAs means that biodiversity conservation success depends on protecting native vegetation on private lands.

̽��ֱ��highest priority landscapes, some 33% of land in the region, are those that either just dipped below the 43% threshold in 2010, or are expected to in the next 20 years.

“Avoiding deforestation and focusing reforestation in the areas that teeter on the species loss threshold will be the most direct and cost-effective way to prevent further species loss in the Amazon region,” added Ochoa-Quintero.

Inset image: Local farmer with a Scarlet Macaw (Credit: JM Ochoa-Quintero)

One of the largest area studies of forest loss impacting biodiversity shows that a third of the Amazon is headed toward or has just past a threshold of forest cover below which species loss is faster and more damaging. Researchers call for conservation policy to switch from targeting individual landowners to entire regions.

We need to move from thinking in terms of compliance at a farm scale to compliance at a landscape scale if we are to save as many species as we can from extinction

Jose Manuel Ochoa-Quintero

Corn plantation nearby remaining forest in the Amazon region

̽��ֱ��text in this work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page. For image rights, please see the credits associated with each individual image.

Yes

Amazonia at a crossroads

sj387 — Thu, 17 Oct 2013 08:00:04 +0000

̽��ֱ��numbers associated with the Amazon are truly staggering. It encompasses nine countries; contains at least a tenth of the known species in the world; provides a home and resources to 31 million people; stores the equivalent amount of carbon to a decade of human-induced emissions for the entire planet; and discharges a fifth of the world’s fresh water.

However, rapid social and ecological change, borne on the back of deforestation, harvesting of natural resources and a changing climate, has left the future of the world’s largest remaining tropical forest uncertain – Amazonia, today, is “standing at a crossroads”, as Dr Toby Gardner describes.

He points to the existence of tough trade-offs that underpin the region’s challenges: “ ̽��ֱ��demand for land and natural resources is driven by the development needs of one of the world’s largest emerging economies, as well as by the insatiable global food and commodities market. Understanding what management practices can best achieve both economic development and environmental conservation is central to addressing this challenge and shepherding the creation of a more sustainable Amazon.”

Gardner leads a new research programme that is motivated by helping to solve this dilemma – the Sustainable Amazon Network – alongside colleagues at Lancaster ̽��ֱ��, the Goeldi Museum in Belém (Brazil) and the Brazilian Agricultural Research Corporation (Embrapa), with funding from the Brazilian and UK governments and ̽��ֱ��Nature Conservancy, among others.

̽��ֱ��Network’s 100-strong group of researchers and students from over 30 institutions are working with conservation organisations, farmers and government officials. Their approach is to assemble an evidence base on the sustainability challenges and ecological consequences associated with land uses and management strategies, and to use this to test the effectiveness and risks of alternative policy choices facing local people and regional governments.

At the heart of the research is an appreciation of the complex array of interactions and feedbacks that characterise the changing face of Amazonia. ̽��ֱ��project takes as its ‘laboratory’ two regions of the eastern Amazon: Paragominas, a region infamous for lawlessness, violence, land grabbing, illegal sawmills and rampant forest clearance until the 1990s; and Santarém-Belterra, once a centre of pre-Colombian civilisation, with a long history of farming and now home to smallholder farms and larger agricultural enterprises.

What makes the project distinct from many other research initiatives is the collection of matched data from the same network of landholdings on changes in both the ecological and the socio-economic characteristics of different land and forest use systems. ̽��ֱ��team’s survey design has enabled information to be collected across the full wealth spectrum, from the poorest to the richest farmers, while allowing comparisons at multiple spatial scales – between different farms, catchments and regions.

̽��ֱ��result is one of the most comprehensive field assessments ever undertaken in the tropics. Critical issues that are being addressed include the identification of potential threshold effects of deforestation on the degradation of ecological systems, and the identification of strategies at both farm and municipality scales that can effectively reconcile conservation and development goals.

“In addition, one of the longer term implications of any initiative like this is the fact that a large group of students and researchers, many of whom are Brazilian, have been exposed to new ideas and new ways of thinking about sustainability problems, and this, perhaps above anything else, will be the most valuable legacy of our project,” added Gardner.

Can the world’s largest tropical forest biome be transformed into a sustainable ecological system? “There is a short window of opportunity and there is potential for recovery,” said Gardner. “But we cannot afford to be complacent.”

̽��ֱ��Amazon rainforest faces an uncertain future – one that an international research network hopes to help steer towards sustainability.

There is a short window of opportunity and there is potential for recovery, but we cannot afford to be complacent

Toby Gardner

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

Yes