By Morgan Erickson-Davis
Nations are hurrying to reduce greenhouse gas emissions and slow global warming, and one way they’re going about this is by encouraging the protection of forests. Trees trap carbon in their biomass and in the soil, and it’s hoped that keeping them in the ground will keep their carbon out of the atmosphere.
Climate-focused forest conservation policies and programs tend to be focused on rainforests. Covering vast areas, rainforests have earned the moniker “lungs of the planet” for their ability to sequester carbon dioxide while producing oxygen.
But pound for pound, other types of forest give rainforests a run for their money. A hectare of mangrove, for instance, can store four times more carbon than can a hectare of rainforest. And now, new research shows that even temperate forests in cities may be able to sequester nearly as much carbon as a similarly sized area of rainforest.
The study was conducted by a team of scientists from University College London, who mapped the carbon stores of areas of tree cover in the London Borough of Camden. Their results were published recently in the journal Carbon Balance and Management.
The team used remotely sensed LiDAR (which stands for “Light Detection and Ranging”) data that provided high-resolution information about tree structure. Armed with specific numbers on the dimensions and extent of Camden’s aboveground biomass (i.e., the parts of trees that aren’t underground), the researchers were able to estimate how much carbon is contained in each pocket of urban forest.
“Urban trees are a vital resource for our cities that people walk past every day,” said lead author Phil Wilkes. “We were able to map the size and shape of every tree in Camden, from forests in large parks to individual trees in back gardens. This not only allows us to measure how much carbon is stored in these trees but also assess other important services they provide such as habitat for birds and insects.”
Their results indicate Camden’s trees contain more carbon than estimated by previous studies. And while, as a whole, the borough’s median carbon density is on the low side when compared to many natural ecosystems – roughly equivalent to subtropical steppe – its urban forests are carbon storage powerhouses. The maximum value they uncovered was in a large, 320-hectare park called Hampstead Heath. There, carbon density approaches that of tropical rainforest.
By Fiona Harvey and Sandra Laville
The first national ‘tree champion’ is charged with reversing the fortunes of the country’s woodlands and beleaguered urban trees.
England is running out of oak. The last of the trees planted by the Victorians are now being harvested, and in the intervening century so few have been grown – and fewer still grown in the right conditions for making timber – that imports, mostly from the US and Europe, are the only answer.
“We are now using the oaks our ancestors planted, and there has been no oak coming up to replace it,” says Mike Tustin, chartered forester at John Clegg and Co, the woodland arm of estate agents Strutt and Parker. “There is no oak left in England. There just is no more.”
Earlier this month, the government appointed the first “tree champion”, who will spearhead its plans to grow 11 million new trees, and conserve existing forests and urban trees. Sir William Worsley, currently chairman of the National Forest Company, has been given the task of overseeing trees in England and Wales, including England’s iconic national tree, and ensuring that trees are not felled unnecessarily. Worsley is a former chief of the Country Land and Business Association, which represents landowners and rural businesses.
In July 2014, DECC published the Bioenergy Emissions and Counterfactual (BEAC) model, which investigates the impact on carbon emissions of various ways of sourcing woody biomass from North America to produce electricity in the UK. The calculator estimates the greenhouse gas intensity by taking into account the counterfactual land use for the scenario (i.e. what the land or wood would have been used for if it was not used for bioenergy). BEAC shows that some scenarios could save considerable carbon emissions compared to fossil fuels, whilst if others occurred they could cause emissions greater than fossil fuels. BEAC did not assess the likelihood of particular scenarios so, in spring 2015, DECC commissioned an independent study (led by Ricardo-AEA and including North American forestry experts) to assess the likelihood that the most carbon intensive BEAC scenarios are happening now or if they might happen in the future, and what might drive or constrain them.
The study found that the majority of the high carbon scenarios identified in the BEAC report are unlikely to occur, but there are four that may be already happening or may happen in the future, although their scale is likely to be limited or uncertain.
The research identified economic decision making as driving forestry practices: the main value of a tree is in sawtimber, not biomass for wood pellet production. It is therefore unlikely that demand for biomass would cause foresters to change behaviour to harvest sooner than they intended, or to switch to supplying wood for bioenergy, but they may increase the intensity with which they manage forests.
Wood pellet imports to the U.K. fell 24 percent year-over-year in August after record high imports during the first half of 2016, but are expected to reach a new all-time high this year, according to the North American Wood Fiber Review.
The UK’s renewable energy industry has hit back at new economic analysis which finds that biomass power could be causing more carbon pollution than burning coal or natural gas, claiming it is “distorting the facts”.
A study released today (17 October) by US-based environmental organisation the Natural Resources Defense Council (NRDC) examines the ‘full system costs’ of wind and solar energy relative to biomass for replacing coal and meeting the UK’s clean energy targets for the period 2020-25.
Considering the latest technology costs; the cost of ensuring reliability of supply, and carbon costs, the NRDC concludes that wind and solar power are likely to be less expensive than burning trees for biomass, and that many forms of biomass – such as that from forests – have been producing higher carbon emissions than coal and natural gas for decades.
However, the report has been discredited by the Renewable Energy Association (REA), which in 2013 founded the Wood Heat Association to support the modern wood heat & biomass generation.
The REA’s head of policy and external affairs James Court told edie: “It is a shame that yet again, misleading reports are fundamentally distorting the facts with a misunderstanding of how the biomass industry works. The REA and wider industry are always eager to engage with any report into the carbon savings that biomass can achieve, something this organisation did not try to obtain.”
The Forestry Commission has issued a Research Note which explores the benefits and drawbacks of converting non-native planted woodlands to native woodlands.
The note also evaluates woodland owners’ and managers’ attitudes towards, and experiences of, conversion.
Increasing the area of native woodlands, including the conversion of non-native conifer woodland to native woodland, where appropriate, is an aim of the UK Forestry Standard Guidelines on Biodiversity.
The Research Note reports that attitudes and experiences vary according to owners’ objectives. Managers whose primary objective is conservation are prepared to invest time and resources converting their woodlands. However, those whose primary objective is timber production are reluctant to pay for conversion because they can be concerned that it will reduce productivity, especially where competition, herbivory and biosecurity threats to native tree species are a potential issue.