Wildlife UK Forum - Discuss the UK countryside and wildlife

Just about everyone now believes that climate change is happening, that this is due to an increase in greenhouse gases (GHGs) in the atmosphere, and that we are the main cause. The most important GHG is carbon dioxide and trees have a key role to play because they capture CO2 from the air during photosynthesis and store carbon as they grow. Between 15% and 30% of a tree (by volume) is carbon, the figure depending on wood density and moisture content. After felling, carbon continues to be locked up in wood products and is eventually returned to the atmosphere through decay or combustion.

Forests are vital in the global struggle to contain climate change. It is estimated that around 20% of annual GHG emissions are caused by de-forestation, and tree planting projects in developing countries are encouraged under the Kyoto protocol.

Carbon in Trees and Woods

Carbon is stored in trees, woodland vegetation and soils. In most UK lowland situations the largest of these stores is the tree itself, including leaves, branches, stems and roots. A mature broadleaved woodland might contain around 200 tonnes of carbon per hectare (80 tonnes per acre) in above ground biomass. Where the woodland is long established the soil might contain as much carbon as the trees and on peaty soils the amount of carbon can be even greater.

Carbon in Wood Products

The total amount of carbon stored in wood products (mainly in houses) in the UK is estimated to be around 80 million tonnes, which represents around half of the amount stored in UK forests. What is important is the longevity of the wood product – an oak beam can lock up carbon for several hundred years. A further benefit of wood products is that they can substitute for materials such as concrete, brick and steel which have much higher embedded energy (the amount of energy that was used in their manufacture). And using wood as a renewable fuel, replacing fossil fuels, has significant carbon benefits provided the woodland is sustainably managed. So is it best for woods to be managed? An unmanaged wood, left to its own devices, will tend to have higher amounts of carbon stored in the trees than a wood where thinning and felling takes place. But you have to account for the amount of carbon that's going to be stored in the wood products, and the reduced carbon emissions through material and fossil fuel substitution. The carbon gains associated with a well (sustainably) managed wood will be greater than for an unmanaged one.

Hello Timbo, welcome to Wildlife UK.

I certainly believe GW is taking place. Deforestation, especially in places such as the Amazon is definitely no helping the cause at all. When you say that wood stores CO2, does that then not mean that once the wood is burnt it is returned to the atmosphere, which could be a problem if used as a fuel?

Unfortunately it isn't quite as simple as that. Growing plants and trees give off greenhouse gasses too. In addition to this dead and dying wood gives off greenhouses too. Burning it just releases it more quickly...more or less straight away. Well managed woods can help to use CO2 as well as releasing it so it gives optimum balance.

Here is a recent article by the scientist who are analyising this issue:

An unexpected and startling discovery that plants emit millions of tonnes of greenhouse gas methane every year has plunged climate change discussions into disarray.

Trees and plants emit up to 30 per cent of the world's methane, Frank Keppler at the Max Plank Institute for Nuclear Physics, Heidelberg, Germany, and his colleagues claim. After discovering that fallen leaves, or plant litter, produced methane, Keppler investigated whether living plants also produce this highly reduced gas in air - an oxygen rich environment. He calculated that plants give off between 60 and 240 million tonnes of methane per year.

The news has shocked the atmospheric science community. 'I'm still amazed that people haven't seen it before,' said David Lowe, from the National Institute of Water and Atmospheric Research, Wellington, New Zealand. 'You wouldn't expect methane to come from plants and the air. You won't find any chemical reaction that people know about that would do that.'

Ed Dlugokencky from the US National Oceanic and Atmospheric Administration expects most scientists to react with disbelief. 'Since plants produce hydrocarbons such as isoprene and terpenes in large amounts and single carbon compounds such as methyl halides and methanol, I should not be too surprised by this result,' he told Chemistry World. Both Lowe and Dlugokencky commented that Keppler's experiments were so thorough there can be little room for doubt about the validity of Keppler's claims.

'It is a new pathway of [methane] formation,' said Keppler, 'it will change our thinking about plants and their role in climate change.'

Keppler has not yet worked out the details of the reaction. 'We know a possible precursor molecule in plants, for example pectin,' he said, but would not say any more about a possible mechanism.

Under Kyoto protocol rules countries are allowed to use forest sinks to offset emissions. If a country emits lots of carbon dioxide, but plants new forests, it can subtract the carbon dioxide that the trees remove. In light of the news that plants produce large quantities of another greenhouse gas, politicians and scientists will now be scrambling to calculate net carbon emissions from trees.

'If you plant trees to try and remove carbon dioxide from the atmosphere, but the trees are actually producing methane at the same time, then the government departments are really going to have to know what those two levels are - what the net emission or sink would be,' said Lowe. New Zealand's ministry for agriculture and ministry for the environment has already contacted him to discuss an immediate investigation.

Keppler cautions against 'over interpreting' his results. He warns that it is not only net emissions from trees that need to be re-evaluated. Rising temperatures caused by greenhouse gases, and changing atmospheric conditions caused by changing carbon dioxide concentrations will lead to increased methane emissions from plants and emphasise global warming, he told Chemistry World. 'This effect could be much more pronounced than the benefit you get from other [reforestation] programmes,' he said.

Hope this helps to explain why in my view it is vital that we shouldn't just leave woodlands to their own devices and should actively seek to manage them. In addition to this careful management helps to encourage diversity of wildlife and plant life.

Thanks

I am not sure if there is such thing as Global Warming. Statistics show that the weather this time of year was actually hotter 40 years ago than it is now. If anything, it is Global Cooling!

Ithink it is difficult for many of us to say with certainty what is or isn't actually happening. I think it is fair to say that weather patterns are changing and this is causing problems for many animals...humans included. I read a very interesting article the other day where the people who live in Churchill Alaska were laughing about Western European articles about ice melting and Polar Bears having to come to residential areas to eat....this isn't the case at all and the ice is thicker. I think the problems is this issue has been hijacked by politicians who are using it to create a quasi-religious type belief system to keep our minds off what they get up to...this said there is unusual and disruptive patterns. This leads to birds like Cuckoos turning up at the wrong time to plant their egg in other birds nests, etc....hard to know the truth though as we aren't scientists and I've never been to the North Pole!

The problem is that there are so many supposed sources being thrown around as fact, that no one really knows what is truth and what isn't anymore. The only way to know if something is true is to look it up in scientific papers, anywhere else doesn't seem to be a reliable source at the moment.

Locally the temperatures may have dropped slightly, but globally on average they have risen. Not a huge amount, but enough to be worrying.

Do you honestly believe that you can always believe what Scientists say. They rely on grants provided by Governments and big corporation...so often will be swayed in terms of their results. There have ironically been scientific studies on this!?

I think global warming is pure hype by Governments cashing in on recycling etc! There will be another Ice Age soon! Mark my words!

Well I certainly think there is more than meets the eye to Global Warming...we've had all sorts of climate change for millions of years....but it is hard to know the truth? The worrying thing for me is when you get changes in weather it usually ends in various species becoming extinct...I just hope we aren't the next candidates!

One of the most interesting things is that about 30% of all green house gasses by all accounts comes form livestock - cows, etc...perhaps we should all become vegetarians? We don't hear the politicians suggesting this!

I would trust scientists much more than politicians. Of course there are going to be some that aren't honest, but I would argue that big corporations would much rather global warming go away as it costs most of them big money, especially the oil companies.

The most important thing is that people make up their own minds about global warming without relying on third or fourth hand information from the press. All scientific papers (the ones in reputable journals anyway) have to pass a peer review process, so the data and methods of acquiring it should be solid. Journalists and politicians have no such checks. Pretty much all science papers can be found somewhere online for free (NASA's ADS site is a good start) too.