Comments on: AskPablo: Land Use Changes

By: Ru Hartwell

Ru Hartwell — Thu, 02 Aug 2007 16:32:41 +0000

Pablo Hi.
This is a very timely discussion bearing in mind the current controversy that surrounds forestry based offsets.
As you point out, one of the most valid criticisms of carbon offset forestry is that it only provides a short-term store for the absorbed C.At Treeflights we have spent a lot of time trying to improve the ‘permanency’ of the offset that our trees will provide.
We have set up a trust to hold ownership(in perpetuity) of the land on which the trees stand so that if the company fails the trees will still be safe.
We have a long-term management plan for our forests that specifically aims to reduce and delay the flow-back of absorbed Carbon to the atmosphere. The trees we grow are all hardwood species chosen for their future value as timber. When hardwood timber is kept dry it may retain its carbon for thousands of years. Ely Cathedral in England has an oak roof built 1000 years ago and it is still in very fine shape, holding on to its carbon very well, thank you.The oak trees used in its construction were themselves 300 years old when the cathedral was built. This means that they were were sequestering their carbon around 1300 years ago.
When timber is kept saturated in an anaerobic environment, such as under water, it can last even longer. There are Viking long ships in museums in York that had oak keel timbers. These ships were sailing up the east coast of England in the 7th century and 80% of the oak (and their carbon) is still there.
Yes, Methane is a far more destructive ghg than CO2. When we change land-use from methane generating ruminant pasture to carbon hungry forest we have the added benefit of a reduced methane footprint. The land we plant trees on, hitherto was grazed by cows each of which release around 500 litres of methane a day. Some estimates suggest that the worlds cows are more destructive to our climate than all the worlds cars put together.
The best solution all round is to convert pasture to forest then once the trees have done the bulk of their absorption work, we should harvest them and use in ways that delay the inevitable flowback of carbon to the air and then replant the same land with new c-hungry saplings.
Our problem is very simple. We have too much carbon in our atmosphere. Trees have evolved over millions of years to become immensely powerful and efficient at withdrawing carbon from our atmosphere, using only natural processes and with myriad collateral benefits. This is precisely the job that we need doing right now.
The answer is staring us in the face.

By: Pablo

Pablo — Thu, 02 Aug 2007 14:45:08 +0000

The best site for a managed forest may be land that was previously biologically unproductive, such as previously developed areas or brownfields. Former agricultural land would also work well, unless you cut down an existing forest to replace the lost agricultural area.
This column looks only at the climate change impact of land-use. Biodiversity and a multitude of other issues further complicate the matter and must be evaluated for individual locations to determine the best land-use policy.

By: Robert V

Robert V — Thu, 02 Aug 2007 14:31:18 +0000

I find it hard to believe that managed forests with the reduced or eliminated understory is a beneficial land use. Reduce genetic diversity is only one of the detrimental impacts. Of course it is better than most uses but natural reforestation is certianly the best alternative. Of course natural reforestation will not allow for economical harvesting of product whether it be fiber, fuel or food. Lets face it, biomass has an impact and can it really be managed?

By: Jon Gelbard

Jon Gelbard — Tue, 31 Jul 2007 03:46:26 +0000

Hi all -
Couple of keys here.
1. As far as the impact of land use and deforestation, it is huge. Indonesia is now I believe the third greatest emitter of greenhouse gases. Mainly attributable to its high levels of tropical deforestation.
2. If young trees are fast growing and absorb more CO2 than old trees, should we cut older trees down and plant tree farms? The answer reflects the reality that the forest is, indeed, greater than the sum of its trees!
For example, one problem with using tree farms to sequester CO2 is the CO2 that comes out of the soils following logging, even if there are young trees growing there.
In many cases, this outflux of CO2 from soils will be even greater than the amount being taken up by young trees!
Here is a nice little summary of a related study from New Scientist: http://www.newscientist.com/article.ns?id=dn2958
Another issue is into which part of trees the extra absorbed CO2 is being allocated. Scientists are finding that a lot of it is going below ground into fine roots, which are very short lived, and quickly return the carbon to the soil when they die… http://www.eurekalert.org/pub_releases/2004-02/jaaj-cdf020504.php
While these kinds of complexities might leave one’s head spinning when pondering how we can slash human impacts to the global carbon cycle, there’s plenty of things we need to do that are plain as day.
When it comes to land use, I’d say THE major take home is (as somebody noted above) that we REALLY REALLY need to find ways to protect the world’s tropical forests. Both for their CO2 uptake capacity, and for the many other environmental services they provide to people and planet (climate regulation, precipiation…) That means finding a solution to the problem that right now, there are lots of people who need to use the forest to feed their families, and the only way they know is logging – for wood or to clear farmland.
We need to find new ways for these folks can to support themselves and their families. The carbon offsets market is, of course, one such mechanism that has huge conservation development potential – to generate lots of funds to pay people to leave tropical forests standing (even if the whole carbon offsets thing still requires some serious standards and regulation to get it working right). Certified and properly monitored sustainable forestry is another, though even FSC still needs much better compliance monitoring.
For a good summary of how to manage ecosystems to maintain their resilience to climate change, check out WWF’s Buying Time manual: http://www.panda.org/news_facts/publications/index.cfm?uNewsID=8678
Cheers all – great topic!

By: ecogal

ecogal — Tue, 31 Jul 2007 01:53:49 +0000

http://www.sciencedaily.com/upi/index.php?feed=Science&article=UPI-1-20070625-10510400-bc-us-forests.xml
Here is an article that, based on a recent study published in Science magainze, points out that all forests are not created equal. This study shows that (unlike previously thought) tropical forests are larger carbon sinks than their temperate counterparts. So, if you’re buying carbon offsets based on reforestation or well-managed forests, perhaps it would be better to know that those forests are in the tropics.
However, since sequestering carbon in trees is temporary no matter how you look at it, would it be better to offset your CO2 emissions with actual reductions like those traded on the Chicago Climate Exchange?

By: Pablo

Pablo — Mon, 30 Jul 2007 12:27:54 +0000

Mike,
Biomass as a building material is essentially the same as other durable goods, such as furniture. A building will last between 60 and 100 years, at which point the building materials may be sent to the landfill or may have been consumed by fire or termites, all of which will release some carbon dioxide and/or methane.

By: mike

mike — Mon, 30 Jul 2007 11:05:04 +0000

What happens when you use the biomass as a building material?