The promotion of tree plantations as a means of combating global warming has received all kinds of criticism. On the one hand, plantations do not relieve pressures from forests -which are carbon reservoirs- but constitute a direct cause of their destruction. According to a satellite image analysis, in the 1980s, 75% of the new tree plantations in Southern countries in the tropics were made by replacing natural forest that had existed there ten years earlier. This meant an estimated additional release of 725 million tonnes of carbon dioxide to the atmosphere, thus contributing to global warming. On the other hand, when plantations are set up on grasslands they substitute a valuable ecosystem as carbon sink and reservoir. The amount of carbon stored by grasslands should be deducted from the volume of carbon allegedly retained by plantations. Furthermore in some cases -as that of the grassland vegetation of the Andean Paramos- recent studies show that natural ecosystems are more efficient that plantations regarding their capacity of absorbing CO2. Last but not least, the promotion of large scale monocultures under the guise of "carbon sinks" will not but aggravate the social and environmental negative impacts that similar plantations -aimed at producing fibre or wood- cause.

Recently, the UN's Intergovernmental Panel on Climate Change (IPCC) issued a report that can be the coup de grace for the idea of plantations as carbon sinks. According to scientists, planned new plantations will quickly become saturated with carbon and begin returning most of their carbon to the atmosphere through respiration. Since CO2 is the most important greenhouse effect gas, global warming would be accelerated instead of mitigated. These new findings mean a change in the IPCC's previous viewpoint concerning the issue. It had been assumed that as long as CO2 levels in the air went on rising, forest sinks would continue to grow due to the accelerating effect of the so-called "CO2 fertilisation" on photosynthesis. However, CO2 fertilisation may already have reached its maximum and respiration may be about to accelerate. Thus, large-scale tree plantations would in fact aggravate instead of mitigating the greenhouse effect.

The above proves that planting trees to absorb CO2 is no substitute for cutting fossil fuel emissions at source and furthermore, to rethinking the present unsustainable production and consumption model that is threatening life on Earth. In spite of the efforts of their promoters to show them as a panacea, tree plantations are not a solution to the problem but a part of it. (Bulletin November, 1999)

Scientific evidences questioning the effectiveness of tree monocultures as carbon sinks are increasing. In case tree plantations are included in the Clean Development Mechanism of the Kyoto Protocol there is the risk that --as has happened in the past and is still happening-- vast areas of forests and grasslands in the South will be substituted by monocultures based on a reduced number of fast-growing tree species. This would mean a dramatic decrease in the biodiversity of such areas, both considering number of species and complexity of fluxes at the interior of the system.

Two years ago, the 4th meeting of the Conference of the Parties to the Convention on Biological Diversity, that took place in Bratislava, explicitly mentioned the potential impact of afforestation, reforestation, forest degradation and deforestation on forest biological diversity and on other ecosystems and mandated its Executive Secretary "to liaise and cooperate with the Secretariat of the United Nations Framework Convention on Climate Change to achieve the objectives of the Convention on Biological Diversity." The reason for this was that if massive tree plantations were to be implemented under the guise of "carbon sinks" biodiversity would be negatively affected.

Reduction of biodiversity is not only a loss in itself but also means a reduction in their former capability of acting as real carbon sinks. A group of scientists of the Centre for Population Biology of the Imperial College at Silwood Park, UK, proved that declining biodiversity can alter the performance of ecosystems regarding biomass production, nutrient retention, decomposition and carbon dioxide absorption. Using chambers representing different terrestrial microcosms, placed in a specially designed laboratory under controlled conditions of air temperature, relative humidity, soil, etc. --called Ecotron-- the researchers manipulated plant and animal diversity in each chamber, simulating the process of degradation occurring in the real world. Higher-diversity communities consumed more carbon dioxide than lower-diversity ones. The conclusion of the article, published in the prestigious magazine "Nature", is clear: "To the extent that loss of plant biodiverstiy in the real world means a reduction in the ability of ecosystems to fix CO2, we also tentatively conclude that the loss of diversity may reduce the ability of terrestrial ecosystems to absorb anthropogenic CO2". (Bulletin October, 2000) 

A recent study of the Tellus Institute and Stockholm Environment Institute-Boston Center concludes "that while the CDM could induce some legitimate lower-emission electricity generation in host countries, it could also give rise to a considerable amount of spurious emissions allowances by crediting non-additional ("free-rider") activities --activities that would have taken place even in the absence of the CDM." The research finds "that under some plausible CDM regimes, the CDM could serve primarily as an instrument for generating spurious credits, and only secondarily as an instrument for economic efficiency or sustainable development."

The most striking finding of this research is the magnitude of the potential free-rider problem. "By intention, the CDM is not designed to reduce global greenhouse gas emissions. CDM projects that reduce emissions in the host countries will generate emissions credits that enable the investor countries to increase their domestic emissions, exceeding their Annex B emissions targets. Thus, at best, if the CDM operates as intended, it will be carbon-neutral on a global scale. However, in practice, to the extent that the CDM generates unwarranted free-rider credits, it will cause a net increase in global carbon emissions."

The researchers argue that "a small flow of free-rider credits might be acceptable, if the overall outcome of the CDM were to help achieve the ultimate objectives of the Climate Convention. This outcome would occur if the CDM catalyzed development and adoption of technologies that could underpin a global transition away from carbon-intensive fuels and contribute to sustainable development. But, in the cases investigated here, it is not evident that the magnitude of potential free-rider credits is justified by the obtained benefits, such as the transfer of some renewable energy technologies to the host countries."

The report's main conclusion "is that free-rider credits from non-additional CDM projects threaten to undermine the environmental integrity of the Kyoto Protocol. Some CDM regimes could lead global emissions to increase by as much as 600 MtC relative to the Kyoto Protocol target, if credits awarded spuriously to projects that would have happened anyways are used in place of real carbon reductions. In economic terms, 600 MtC of free-rider credits would be worth $6 billion at $10/tC or $60 billion at $100/tC. These free riders would amount to a multi-billion dollar cross-subsidy to CDM project participants at the expense of the global environment. It is therefore imperative that policy makers devise and adopt a CDM regime that effectively encourages legitimate projects, while rigorously screening out non-additional activities." (Bulletin October, 2000)

The International Institute for Applied Systems Analysis (IIASA), based in Laxenburg, Austria. carried out a detailed study of Russia's biosphere, which contains a fifth of the world's forests. Its report puts in question the whole idea of using carbon sinks as a means of "compensating" for CO2 emissions. Anatoly Shvidenko, one of the scientists involved in the study, stated that under the Kyoto Protocol, Russia is likely to be able to claim credit for improving its biosphere's ability to soak up carbon, but that the uncertainties involved in calculating such credits are huge and "greatly exceed likely changes in industrial emissions."

Sten Nilsson, also from IIASA, concluded that "the scientific uncertainties in measuring carbon movements into and out of ecosystems are just too great," and that "by opening up the whole of the biosphere to actions under the Kyoto Protocol, governments have made it completely unverifiable." IIASA's Michael Obersteiner summarized the whole issue by saying that the Protocol "really is a cheat's charter."

Asked to comment on the IIASA report, a US analyst of the Kyoto Protocol, David Victor, working at the New York-based Council on Foreign Relations, concurred with its findings. "Their analysis is fundamentally correct. It is essentially impossible to verify compliance if the targets include forests," Victor said.

After analysing the IIASA report and other relevant information and viewpoints, "New Scientist" journalist Fred Pearce reaches the conclusion that "the message from the IIASA seems clear. Science is not yet up to policing a system of greenhouse gas targets that includes the biosphere. Until it is, the only viable Kyoto Protocol is one that relies solely on slashing the world's use of fossil fuels." (Bulletin October, 2000)

During the climate change discussions, some have argued that, given that old-growth forests are carbon reservoirs --and not carbon sinks-- the world's climate would benefit from cutting them down, converting the wood into durable products and replanting the clearcut area. The existing carbon would be safely stored in wood products and the plantation trees would act as sinks for many years, until they reached maturity. This would enhance --so they say-- the carbon sink capacity of forest ecosystems.

Apart from the many flaws of such approach, a recent study has shown the importance of old-growth forests as carbon sinks and has warned against their substitution by plantations. The research concludes that forests are far better than plantations at ridding the air of carbon dioxide. The analysis, published in the journal Science, was carried out by Dr. Ernst-Detlef Schulze, the director of the Max Planck Institute for Biogeochemistry in Jena, Germany, and two other scientists at the institute.

The German study, together with other similar research, has produced a picture of mature forests that differs sharply from long-held notions in forestry. Dr. Schulze says that aging forests were long perceived to be in a state of decay that releases as much carbon dioxide as it captures. But it turns out that the soils in undisturbed tropical rain forests, Siberian woods and some German national parks contain enormous amounts of carbon derived from fallen leaves, twigs and buried roots that can bind to soil particles and remain there for 1,000 years or more. When such forests are cut, the trees' roots decay and soil is disrupted, releasing the carbon dioxide. Centuries would have to pass until newly planted trees built up such a reservoir underground.

The study's authors stress the need to protect old-growth forests. Without such protection, the scientists conclude, some countries could be tempted to cut down old-growth forests now and then plant new trees on the deforested land, getting credit for reducing carbon dioxide when they have actually made matters worse.

Several climate and forestry experts familiar with the work have said the study provided an important new argument for protecting primary forests. They add that the study also provides a reminder that the main goal should be to reduce carbon dioxide emissions at the source. (BulletinOctober, 2000)