Week 1 | Q’s 3,4,5: The Role of Forests in Global Climate
September 18th, 2009 at 11:27by Joannes Paulus Yimbesalu
Hello Group,
I am sorry for the delay in participation. I was so busy with other work and now I am quite free to take part actively in this wonderful conversation. The conversation is so wonderful and I feel happy that we are discussing issues that affect our environment, our climate and our world.
In a study to be published next week in the Proceedings of the National Academy of Sciences,scientists led by a team at the University of New Hampshire show that forests may influence the Earth’s climate in important ways that have not previously been recognized.
When sunlight reaches the Earth’s surface it can either be absorbed and converted to heat or reflected back to outer space, where it doesn’t influence the Earth’s temperature. Scott Ollinger, a professor at the UNH Institute for the Study of Earth, Oceans, and Space and the department of Natural Resources and the Environment, and colleagues have discovered that, of the total amount of sunlight that falls on forests, the fraction that gets reflected back to space is directly related to levels of nitrogen in their foliage.
While scientists have long known that nitrogen-rich foliage is more efficient at pulling carbon dioxide out of the atmosphere, this new discovery suggests that nitrogen plays an important additional role in the Earth’s climate system that has never before been considered. Specifically, trees with high levels of foliar nitrogen have a two-fold effect on climate by simultaneously absorbing more CO2 and reflecting more solar radiation than their low-nitrogen counterparts.
Ollinger and UNH colleagues Andrew Richardson, Mary Martin, Dave Hollinger, Steve Frolking, and others, stumbled upon the discovery while poring over six years worth of data they collected from research sites across North America. The study involved a novel combination of NASA satellite- and aircraft-based instruments, along with meteorological towers from the AmeriFlux network and leaf-level measurements to analyze various aspects of forest canopies. When Ollinger noticed that the overall reflectivity of forest canopies (also known as albedo) rose and fell in conjunction with leaf nitrogen, he had a eureka moment.
“Bits and pieces of evidence for this have been around for years but nobody put them together before because it’s a question we hadn’t even thought to ask,” Ollinger says. “Scientists have long been aware of the importance of albedo, but no one suspected that the albedo of forests might be influenced by nitrogen. And because most of the effect is in the infra-red region of the sun’s spectrum, beyond that which human eyes can detect, the pattern isn’t immediately obvious.”
The newly discovered link between foliar nitrogen and canopy albedo adds an interesting new twist to the understanding of the climate system and raises intriguing questions about the underlying nature of ecosystem–climate interactions.
Changes in climate, air pollution, land use, and species composition can all influence nitrogen levels in foliage, and all of these may be part of a climate feedback mechanism that climate models have not yet examined. Future research planned by the team will involve examining the underlying causes for why the relationship exists and working with climate modelers to determine how the nitrogen-albedo mechanism will influence predictions of climate change.
September 18th, 2009 at 11:54 am
This is an excellent post Joannes! To our syllabus I added a great lecture that reviews forest nutrient cycles.
When discussing climate and forests we often consider physical and chemical regulations. Of the chemical components, we hear about Carbon (C), Nitrogen (N) and Phosphorus (P) the most. Nitrogen and Phosphorus are often in much shorter supply than Carbon. Therefore, N and P are critical to growth because they are harder to ascertain (they are in shorter supply). Carbon is abundant, so removal of forests releases quite a bit. Our paper from Cramer (et al, 2004) discusses the role of forests in relation to Carbon.
Like the oceans, forests absorb carbon at higher rates than other ecosystems. In general, forests are high absorbers of most terrestrial chemicals/nutrients, and therefore the destruction releases greater amounts of these elements. In turn, these elements literally wash into other ecosystems and affect the nutrient cycle. Release into the ocean and into the atmosphere affects climate.
We can use this post by Joannes to answer the remaining questions for this week, as they all relate to the effects of forest on climate, soils, and water.
>What role do healthy forests play in the regulation of the global climate?
>Does deforestation jeopardize climate processes? How can this be determined?
>What effects does deforestation have on the terrestrial environment (soil and groundwater)?
September 18th, 2009 at 3:29 pm
Thanks Alison
I am happy that you are happy with my post and I think it will help a great deal in answering the other 3 questions you just mentioned. I promise to do my best in contributing positively to the forum.
have a great day I will use thsi opportunity to say hi to all the other team members
Paulus
September 22nd, 2009 at 1:05 am
Perhaps the greatest impact healthy forests play in the regulation of climate is related to water. Plants take up water and nutrients through their roots and up into their leaves. Transpiration allows water vapor to escape into the atmosphere to form clouds, which in turn rain upon the forest. When trees are removed, less water is taken up and runs off the land, sometimes to distant streams, causing a drying trend in the forest. Along with water runoff is the loss of nutrients that leach away in flash floods from water not taken up by the trees. Nutrients are also lost due to erosion from roads necessary for the harvest of trees.
Tropical rain forests have decreased by nearly ½ since 1975 as shown in satellite data. The tropical rain forest in Brazil’s Amazonia accounts for 30% of the world’s forests. Forest Fires emit greenhouse gases and CO2 emissions for Brazil has nearly doubled in the past 20 years. Slash-and-burn agriculture, used both for subsistence and speculative farming (i.e beef industry) converts forest to farm land. Smoke hangs over the forest and suppresses rainfall. In this damaged landscape, the beginning of the natural dry season becomes ominous.
September 22nd, 2009 at 6:23 am
just a quick question regarding something in the U Michigan lecture. It says
“Tropical deforestation contributes as much as 90% of the current net release of biotic carbon dioxide into the atmosphere. This change may represent as much as 20% – 30% of the total carbon flux due to humans – i.e., rivaling the carbon release due to fossil fuel burning.”
Tropical deforestation seems like a human endeavor (like burning fossil fuel) yet they say it contributes up to 90% of BIOTIC carbon dioxide release… doesn’t BIOTIC here refer to ‘naturally’ occuring CO2 release?
Then it goes on to compare this number to human related CO2 release– can anyone clarify the biotic vs. human caused CO2 release?
Thanks!
September 22nd, 2009 at 7:30 am
It is quite obvious, based on the resources provided here and other sources of information, that halting the spread of deforestation in tropical climes and otherwise is absolutely essential to try and cap greenhouse gas emissions, and then draw down. U.N. I.P.C.C., amongst other scientific organizations, has said that deforestation accounts for around one-fifth of global emissions (deforestation for the purposes of agriculture, biofuel growth, etc). This figure does not take into account the greenhouse gases that are emitted- methane, CO2- from cattle that are often made to graze the deforested lands of tropical regions. If you were to halt the spread of deforestation, you could help kill two ‘climate’ birds with one stone by halting the raising of livestock in deforested areas.
Healthy forests helping to regulate climate change has also taken on a 21st century economic angle in the form of possible offsets/ payments from richer (economically) nations to “developing” nations to protect and/or reforest devastated areas. In climate change ‘cap and trade’ legislation currently pending in the U.S., 5% (from 2012 to 2025) of the proceeds from carbon allowances given to polluting industries and then subsequently sold are earmarked for deforestation efforts. Say what you want about the economic motive, but this could provide billions of dollars for developing nations’ governments to save their tropical and other forests and does achieve a climate change end. I say increase the funding!
http://climateprogress.org/2009/06/29/tackling-climate-change-by-saving-forests/
September 23rd, 2009 at 12:13 pm
Scientific terminology can often defeat it’s purpose by being too redundant. In the U Mich lecture, “biotic” co2 release refers to co2 deposited into the atmosphere by decay (what the ground releases when the trees are cut and root communities die). Abiotic co2 release would be humans using biotic oils and mechanically releasing them through industry, etc.
I hope this illuminates the variation in terminology.
July 29th, 2010 at 11:38 pm
Hello,
I am writing with regards a course I took from P2PU some months back. I think the course was on Land Restoration an Afforestation. This course came to an end and since then I have been waiting for a Certificate of recognition till now but have had none. I dont know if you guys sent it to me already or still planning on sending it.This course was been coordinated by Alison Jean Cole. I will be happy to read from you with regards this.
have a great day then