Almost half of Asian trees in regeneration projects die in five years
NEARLY half of all the trees planted as part of restoration programmes in tropical forests in Asia do not survive more than five years, Scottish research has revealed.
A team of international experts from 29 universities and research centres, including scientists from the UK, analysed data from 176 forest restoration sites in tropical and sub-tropical Asia, where human activities have caused trees to decline.
They found that 18 per cent of saplings died within the first year of being planted, while after five years the figure was 44%.
But the team also found that survival rates varied between sites and species, with some sites seeing more than 80% of trees still alive after five years, while other sites saw almost all the trees die.
The researchers said their findings, published in the journal Philosophical Transactions of the Royal Society B: Biological Sciences, indicate that using a tailored approach may be needed to restore forests and make them successful.
Study author Dr Lindsay Banin, from the UK Centre for Ecology & Hydrology, said: “What’s clear is that success is very site-dependent – we need to understand what works and why and share that information, so we can bring all sites up to the level of the most successful and harness the full potential for restoration.
“There’s likely no one-size-fits-all approach and restoration action should be tailored to local conditions.
“This will help ensure the scarce resources and land available to restoration are used to best effect.”
South-east Asia’s forests are among the most carbon-dense in the world – accounting for 15% of the world’s tropical forests.
These regions are also very species-rich, providing habitat for tigers, primates and elephants.
But, in the last few decades, these places have seen major deforestation – with forest cover reducing by an estimated 32 million hectares between 1990 and 2010, the researchers said.
The researchers found that reforestation efforts were less successful than in areas that have been fully deforested.
Meanwhile, saplings planted in areas with existing mature trees were found to have around 20% higher chance of survival.
The researchers said there is evidence suggesting that active restoration provides faster results than simply letting nature take its course.
But more studies tracked the fate of planted trees, the experts added.
Study co-author David Burslem, a professor at the University of Aberdeen, said: “We need to understand better how to improve the survival chances of saplings on these sites, to ensure restoration has positive outcomes.
“But the study also provides a warning, to protect our remaining forests as much as possible, both because restoration outcomes are uncertain and to provide the diverse seed sources needed for restoration activities.”
Reforestation is one of the key ways to tackle the loss of biodiversity as well as climate change, and planting trees is often used widely for carbon offsetting, which means compensating for carbon dioxide emissions arising
from industrial or other human activity.
Meanwhile, Scottish campaigners are celebrating a “major victory” in the battle to save Scotland’s disappearing ancient woods due to the change of a single word.
A proposed policy tabled in the Scottish Parliament would bar developments that would destroy or damage rare habitats and individual ancient or veteran trees.
Previous drafts of the planning rules stated such woodland “should not” be lost to development. The new wording states such developments “will not” be supported.
The charity Woodland Trust Scotland hopes that, once implemented, it is likely to guide planning procedures within Scottish local authorities for the coming decades.
Suzie Saunders, policy advocate for Woodland Trust Scotland, said: “Precision of language means everything in policy like this.
“The switch from ‘should not’ to ‘will not’ could be the most important change in ancient woodland
protection for years.” Planning Minister Tom Arthur laid the revised draft of National Planning Framework 4 before parliament last week to commence scrutiny which will run until December 20.
The section covering forestry states: “Development proposals will not be supported where they will result in: any loss of ancient woodlands, ancient and veteran trees, or adverse impact on their ecological condition.”
Campaigners believe that the crucial change offers watertight protection for rare and precious habitats in Scotland.
Ms Saunders added: “This is our richest and most complex terrestrial habitat with vast plant, animal and fungal communities developed over centuries with minimal disturbance. “They are irreplaceable.
“You cannot just plant trees in a field and expect the complex biodiversity built over centuries to take up residence.
“Once they are gone, they are gone for good, so it has been a matter of huge concern that the little we have left has been chipped away at over the years for things like building
developments, car parks and golf courses.”
Ancient woods in Scotland are defined as those that have persisted on maps since at least 1750.
Only around 1.9% of Scotland’s land area remains as ancient woodland. Left relatively undisturbed by human development, they are home to unique and complex communities of animals, plants, fungi, insects and other microorganisms that have developed over centuries.
However, hundreds of these woods have been put under threat from built development in recent years and many suffered loss or damage, often at the expense of native species.
Saunders said: “Woodland Trust Scotland has long campaigned for an absolute moratorium on developments which destroy or damage these remaining patches.the consultation on a new National Planning Framework was a major opportunity to call a halt to the destruction and we are absolutely delighted that the voice of our members and supporters has been heard loud and clear in Parliament.”
Restoration action should be tailored to local conditions