Voluntary carbon offset schemes using forest plantations are being increasingly used by governments and states despite an increase in drought and disease affecting forests that raises concerns about their reliability.

A new survey of 15 national and sub-national government agencies around the world that have incorporated voluntary climate change offsetting into their strategies shows that their use is on the increase.

Many of these schemes use the planting of woodland or forests to claim an amount of carbon dioxide sequestration equivalent to that emitted elsewhere.

In Britain, the Forestry Commission last year set up the Woodland Carbon Code for this purpose, even though the Commission itself confesses that it is worried about the impact of climate change on its own forests.

The report, by Ecosystem Marketplace, an American grouping of financiers and environmentalists, says that the prices for credits generated under these offsetting programmes averaged $11 per ton of carbon dioxide equivalent (tCO2e), compared to a global average of $6 per ton.

It believes that participants prefer them to the “top-down methods" pursued by the United Nations Framework Convention on Climate Change (UNFCCC), finding that 6.3 MtCO2e was transacted by respondents to its survey in 2011, and that governments anticipate that in the next three years another 48MtCO2e will be transacted, showing that the trend of using voluntary offsets is increasing.

The survey covers 13 states, all but one of which are using forestation to offset carbon emissions. Those allowing the development or purchase of forest carbon credits are: Oregon, California, British Columbia, Oklahoma, Japan, Thailand, China, Australia, Costa Rica, the United Kingdom, Italy, and the Netherlands.

The Woodland Carbon Code

The UK Forestry Standard sets out the government's approach to sustainable forestry.

Its official position is that "forest management should contribute to climate change mitigation over the long term through the net capture and storage of carbon in the forest ecosystem and in wood products".

The Forestry Commission's Woodland Carbon Code (WCC) sets standards for claims about the carbon sequestered by woodland projects.

Though WCC projects can’t generate official government offsets due to the problem of double-monetisation, the Forestry Commission’s Pat Snowdon says the WCC shares many features with international standards, like a buffer pool, project grouping mechanism and independent certification.

In 2011, the Department for Environment, Food, and Rural Affairs (Defra) updated its emissions reporting guidance to allow organisations to “net out” WCC credits from their total gross emissions, a move that is described by Ecosystem Marketplace as "a significant recognition of market-based private sector climate action on the part of a national agency".

But since the issue of double counting “remains a significant barrier to investment”, according to one stakeholder, the Forestry Commission is in discussions with credit agency Markit Environmental Registry about listing a “Woodland Carbon Unit” on its independent carbon unit registry system.

Pat Snowden says this would be "good for transparency, to avoid double accounting. Markit is well-respected".

He says the the FC, "as part of government, is helping to get the voluntary market going. We are not acting as a broker, that's for the sector, but we will signpost people to help market get going".

They have been training the two certification partners, overseen by UKAS. One of these is SGS UK, a risk assessment business used extensively by the oil industry, also responsible for independent assessment of the environmental performance of the 2012 Olympic Games.

The value of this young market is "potentially huge globally," Snowden told EAEM. "It will be good for the UK's environmental impact investment market. Companies want to invest not just for economic reasons, but for CSR. They like the fact that clients can come and see the forests in this country."

He said a recent report by JP Morgan estimated the global market to grow to $500bn over the next five years. "We've seen lots of interest," he added.

So far, 60 tree-planting carbon offset projects are registered on WCC's website, covering 3000ha, a significant number given it is less than one year old; but only eight of these have actually been validated.

Plantations registered under the scheme will be regularly inspected every five years to determine whether the anticipated total sequestration of carbon is actually occurring.

The Forestry Commission uses a figure of 5.4 tonnes of carbon dioxide absorbed by forests per hectare per year.

To safeguard the CO2 absorbed, the trees should be harvested and stored at their peak growth to prevent it being re-emitted as the tree gradually rots and dies. The precise timing of this depends on the tree species.

Risk of disease and drought

However, the UK's national Climate Change Risk Assessment published last January by Defra observes that climate change in Britain and elsewhere in the world is likely to result in drought and disease which could kill or impair forests.

It says in particular that "the productivity of commercial tree species could change due to drought, and declining timber yield is particularly likely in England, where, without measures to prevent it, it could decline by between 10 and 25% in South East England by the 2080s".

Moreover, there is “an increasing threat to trees and woodland from tree pests and diseases, many of which are likely to thrive in warmer conditions".

This is already happening. On 9 February, the Forestry Commission issued an alert that Phytophthora austrocedrae, a fungus-like organism, had been found infecting Juniper trees in Teesdale.

They called it “especially serious".

Diseases are also attacking Yew and other trees, and last year, 876 hectares of Japanese larch trees were found to be infected by ramorum disease in Wales.

These are having to be felled and disposed of to prevent them infecting other trees. Woodland owners have found themselves in possession of worthless stock.

Given this, what is the reliability of using forestation to offset carbon if there is no guarantee that the activity will result successfully in carbon being sequestered?

Nigel Dudley, one of the UK's top experts on forestation, ecosystems and protected areas, told EAEM that, “the truth is that no one really knows whether using forests to offset carbon is really effective.

"That's because we can't be sure what effects climate change is going to bring. That's why designers of these schemes should build in significant safety margins, just in case areas of the forest do die."

“Of course, planting forests has many other values, but if the worst predictions of climate change come true, then planting forests to offset carbon could be a worthless activity," said Dudley.

In response, the Forestry Commission's Pat Snowdon said that WCC approved schemes allow for a buffer amount of 20% for estimation error, plus a risk buffer depending on assessment of site, of say 10-25% giving roughly a 35% total.

"Having a buffer provides confidence in the market," he said. "We think the buffers are quite generous."

Of the Climate Change Risk Assessment, he said that "of course, uncertainty increases further into future. This is what the buffer is designed to deal with. The CCRA has to be open and cautious, and we need to think about what we plant. Some trees could grow better in the future; we should perhaps be planting species of Beech that currently thrive in Southern Europe."

However Snowdon did admit that the Commission has seen "an increase in recent years" of diseases affecting trees. "If we are looking more than 40 years ahead, we have no idea what will happen. Only time will tell".

Renewable energy offsets

The carbon sequestered from the atmosphere inside timber will happen in the future as trees planted in these schemes grow and mature.

But the carbon emitted by the current activities that are being offset, is already in the atmosphere working to increase the greenhouse effect.

It is for this reason that the official UNFCCC climate offset projects under the Joint implementation and Clean Development Mechanism focus on renewable energy and energy efficiency.

Projects registered under these schemes are intended to prevent the emission of global warming gases in the first place.

For the sake of reliability it seems that investing in woodland, while beneficial in many respects, cannot offer cast-iron guarantees for climate mitigation.

Story: David Thorpe, News Editor