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Uruguay: Forestry and climate change. Between speech and evidence

Uruguay: Forestry and climate change. Between speech and evidence


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By Víctor L. Bacchetta

The forestry policy applied in the country, justified as a model of sustainable development that would preserve biodiversity, the quality of soils and water resources, is questioned by international scientific studies and by Uruguayan experts.


"AS AN AGRICULTURAL COUNTRY and in the knowledge that agriculture contributes greatly to the emission of greenhouse gases, (Uruguay) is identified with the application of mitigation strategies for the agricultural and forestry sectors. Thus, in a process which has been going on for more than twenty years, has developed an important afforestation program that today has more than 700,000 hectares of forests planted, an important area in relation to its territory ", argued the secretary of the presidency Miguel Toma, Uruguayan delegate at the last summit of FAO held this month in Rome.

This conceptual framework, shared by FAO, the World Bank and other international organizations, considers tree plantations as very effective 'sinks'. So much so that they include them in the unique ‘carbon trading’, by which companies can offset their polluting emissions by buying pollution-reducing activity titles. Thus, environmental protection would be reconciled with the continuity of the predatory industrial standards in force. But studies do not confirm that claim.

Foresting in grasslands

If a tree plantation is deployed over an area where a primary forest previously existed, one ecosystem is replaced by a relatively similar one. But the problem acquires another entity when the trees supplant an ecosystem of the pampas prairie or grasslands, such as the one that characterizes the soils of Uruguay and neighboring countries. At first glance, the difference seems to tip the balance in favor of afforestation. The volume of biomass in a eucalyptus or pine plantation is much greater than the pasture it replaces. Therefore: it should retain much more carbon. However, studies of plantations in grassland ecosystems, published in scientific journals since 2002, conclude that previous estimates of the amount of carbon storable by trees were overvalued.

Researchers from four universities in the United States published in 'Nature' -in 2002 (1) - the results of a study carried out in that country to determine whether the trees and shrubs that invaded native grasslands helped absorb carbon dioxide emissions. carbon from vehicles, power plants and other sources. The novelty that these investigations contributed is that the soil constitutes a carbon deposit as or more important than plants and trees.

A Duke University team led by biologist Robert Jackson found that trees in many places were absorbing less carbon than was stored by grassland-covered soil. The soil's capacity to store carbon is about twice that of plants, but grasslands can store carbon in the soil for centuries, while trees release it and do not compensate for it with the increased biomass from the plantation. "Assessments based on the carbon stored by the emergence of tree populations may therefore be incorrect," Jackson said at the time.

Combining field research, the synthesis of more than 600 observations and climate and economic models, the same team documented worldwide substantial losses from runoff (water from rain that circulates over the surface and concentrates in streams) and a increasing salinization and acidification of the soil caused by forest plantations in grassland areas. "Carbon sequestration strategies give importance to tree plantations without considering all their environmental consequences," warned the new report published in 'Science' in 2005 (2).

According to this study - which considered plots in Argentina and Uruguay - the tree plantations together reduced the annual surface flow of water by 52 percent. The salinization and acidification observed indicated a loss of soil fertility and the imminence of a desertification process.

Confront data with data

Carlos Céspedes, a researcher at the Uruguayan Faculty of Sciences, in his doctoral thesis (3) analyzed the effects of planting exotic species on prairie soils in Piedras Coloradas-Algorta, one of the most representative forest regions in the country. In particular, he studied the dynamics of organic matter and a series of parameters that measure variations in carbon, acidity and the degree of compaction of the soil in eucalyptus plantations of different ages (10 to 30 years) and also evaluated the effects of the crop ages.


"It was possible to demonstrate the loss of soil carbon under eucalyptus compared to grasslands," Cespedes said. In his opinion, carbon income does not compensate for losses in soil or biomass because forest management - planting, pruning, cutting and replanting - involves a mean time of carbon retention of little value in the global balance. The loss of carbon is accompanied by a fall in most of the parameters studied and is progressive with the age of the crops.

Céspedes said that the different positions in this regard can be attributed to a "caste of technocrats" that has transformed the scientific debate into a matter of opinions. "They never went to the field, they never read serious scientific articles, they do not generate scientific evidence verified by peers, they manipulate data from third parties, but they are international experts, they manage resources. In science, those who speak are the data, you have to have data and confront data with fact".

The first environmental evaluations of forestry (4) - carried out by national authors starting in 1989 from the Interdisciplinary Center for Development Studies, Uruguay (CIEDUR) - anticipated what would later be proven by countless scientific studies inside and outside the country: debasing and acidification of soils, decrease in the average annual yield of forested basins - the surface water tables dry up - and significant loss of biological diversity.

"Already in those reports, eucalyptus was excluded from any benefit in the management of water basins because at the same time that it decreases the water yield of the basins, under certain circumstances, it can promote severe floods", comments Professor Daniel Panario, director of the Epigenesis Unit of the Faculty of Sciences. The study by Céspedes, among others, determined that under a thin layer where the eucalyptus concentrates its superficial roots, the density of the soil increases substantially in relation to its meadow equivalent: "Under these conditions, a so-called exceptional rain of more than 200 millimeters in 24 to 48 hours, but which in recent years occurs frequently, will drain violently, "explained Panario.

For the researcher, considering that this region of the world has the record of increase in rainfall -as a result of global warming- and that most of this increase is due to the passage of fronts with occasionally torrential rains, it is expected that deficits will be combined severe water conditions in summer and possible floods in autumn, such as those that occurred in 2007 in the country (5).

Notes

1. "Ecosystem carbon loss with woody plant invasion of grasslands", Robert B. Jackson, Jay L. Banner, Esteban G. Jobbágy, William T. Pockman and Diana H. Wall, Letter to Nature, Volume 418 Number 6898, pp. 623, 8/8/2002.
2. "Trading Water for Carbon with Biological Carbon Sequestration", by R. B. Jackson, E. G. Jobbágy, R. Avissar, S. Baidya Roy, D. J. Barrett, Ch. W. Cook, K. A.
Farley, D.C. le Maitre, B. McCarl and B. Murray, Science, Vol. 310. no. 5756, pp. 1944-1947, 12/23/2005.
3. "Dynamics of organic matter and some physicochemical parameters in Molisoles, in the conversion of a meadow to forest cultivation in the Piedras region
Coloradas-Algorta (Uruguay) ", Carlos Céspedes Payret, PhD Thesis presented to L´Institut National Polytechnique de Toulouse, France, in November 2007.
4. "Forest development and environment in Uruguay. Towards an evaluation of the environmental effects of afforestation in Uruguay with introduced species", Caffera, R., C. Céspedes, A. González, O. Gutiérrez and D. Panario, CIEDUR
(Investigations Series No. 85), Montevideo, 1991.
5. "The industrial forestation of Uruguay, State Policy?", Daniel Panario and Ofelia Gutiérrez, Montevideo, 2008.


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