̽��ֱ�� of Cambridge - ̽��ֱ��Nature Conservancy

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

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Mangroves could survive sea-level rise if protected

tdk25 — Wed, 31 Jul 2013 07:44:32 +0000

Mangroves, which provide a natural coastal defence to communities around the world, may be able to withstand a future rise in sea levels far more than previously thought, scientists have found.

Their report should serve to allay fears that many mangrove areas could be lost in the coming decades as sea levels go up because of global warming.

It comes, however, with a cautionary note: ̽��ֱ��authors, who have carried out a rare and detailed survey of how mangroves adapt to their environment, also argue that it is vital that they are managed and conserved so that they can continue to provide this protection.

̽��ֱ��survey warns that human activity on land – such as the damming up of rivers or the felling of trees to create shrimp ponds – is currently a far greater threat to many mangrove habitats than the effects of climate change on sea level.

Mangroves – trees and shrubs which grow in saltwater, coastal environments – play a critical role in protecting thousands of shoreline communities in tropical and subtropical regions from floods, storms, and other hazards.

Their densely-packed, overground root systems can absorb wave energy and reduce the velocity of a sudden surge of water. In the 2004 tsunami, for example, mangroves were sometimes the difference between life and death for people whose homes lay in the path of the giant waves which crashed into shorelines around South Asia.

For some time, scientists have been concerned that if sea levels rise as predicted, they will kill off mangroves – removing these natural coastal defences at the very time they are expected to be needed most.

̽��ֱ��new study suggests that this is far less likely than previously thought, however. Dr Anna McIvor, from the ̽��ֱ�� of Cambridge, and the report’s lead author, said: “Although we can expect some mangrove areas to be lost as sea levels rise, many of them appear to be able to withstand it.”

“In fact, changes to mangrove habitats through human activity are likely to pose a bigger threat to these coastal defences than sea level rise as it stands. Our research has enabled us to find out more about how mangroves continue to flourish in spite of a rise in sea levels – but that information should be used as the basis for better management of these important ecosystems.”

̽��ֱ��study was carried out by a team from ̽��ֱ��Nature Conservancy, Wetlands International, and the Cambridge Coastal Research Unit (based in the ̽��ֱ��’s Department of Geography). ̽��ֱ��researchers examined both recent reports looking at surface elevation in mangrove areas, and the historical reasons why mangroves have, in some places, persisted for thousands of years.

They found that the height of the soil surface in mangrove areas is often “surprisingly dynamic”, and in some cases appears to be building up at rates of between one and 10 millimetres every year. ̽��ֱ��global mean sea level rise is currently 3mm per year, meaning that many mangrove areas build up soil at a rate which keeps pace with the sea.

There are several reasons for this, but chief among them appear to be the ability of mangroves to trap sediment as it is carried down to them by rivers, and the work of their roots beneath the surface. “Mangroves provide much of the organic sediment matter that makes up the soil, their complex roots help to bind and trap the sediments on the soil surface, while the unseen growth of roots beneath helps to build up the soil from below,” McIvor said.

Despite this resistance to changes in sea level, however, the report cautions that the future stability of mangroves is by no means guaranteed. “Threshold rates of sea level rise are likely to exist, beyond which mangrove surfaces are no longer able to keep up,” the authors point out.

Perhaps more urgently, in some regions human activities like agriculture and construction are being authorised regardless of their impact on the ecosystems which enable mangroves to thrive.

In some countries, for example, rivers which play a vital role by carrying sediment to the mangrove areas so that the soil can be built up are being dammed or diverted. Another common threat is aquaculture: in Indonesia, and other South Asian countries, mangroves are often cut down without restriction to make way for shrimp ponds.

̽��ֱ��report also warns that mangroves may need room to expand landward, especially where conditions are such that sea level rise may still be a threat to their growth. Communities which rely on them for coastal defence need to leave space to ensure that this can happen, the authors advise.

Dr Mark Spalding, from ̽��ֱ��Nature Conservancy and the Department of Zoology, ̽��ֱ�� of Cambridge, said: “This report shows that well-managed mangroves in many places will continue to support and safeguard many vulnerable communities as sea levels rise. We still have lots to learn about them, but the sensible, precautionary approach is to look after them and restore them as a critical first line of defence.”

̽��ֱ��full report can be downloaded at: http://coastalresilience.org/science/mangroves/surface-elevation-and-sea...

For more information about this story, please contact Tom Kirk, Tel: 01223 332300, thomas.kirk@admin.cam.ac.uk

Human activity is currently a bigger threat to mangroves, and the natural defences they provide against storm surges and other coastal disasters, than rising sea levels, according to a new study.

Although we can expect some mangrove areas to be lost as sea levels rise, many of them appear to be able to withstand it.

Anna McIvor

Wikimedia Commons.

Mangrove trees along a coastline, Everglades National Park.

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