Smithsonian's perspective on impact of global warming on biodiversity
As an extremely diverse region of rainforest and coral reefs, the tropics may have the most to lose as a result of global warming. Some disagree, arguing that tropical organisms will be favored as their ranges expand into temperate areas. Few empirical studies provide specific answers to help us choose conservation and mitigation measures.
Science asked Jens Svenning, University of Aarhus, Denmark and Richard Condit of the Smithsonian's Global Earth Observatory Network to review two papers about species range change.
In a range analysis for plants and insects on a mountain slope in Costa Rica, Colwell et al. show that a 3.2˚ C increase in temperature threatens 53 percent of the area's species with lowland extinction and 51 percent with range shift gaps, meaning that they have nowhere else to go.
The other study they reviewed, by Moritz et al., follows historical range expansions and contractions for small mammals in Yosemite National Park in California, USA and shows that ranges may contract dangerously as they are pushed further and further up mountain slopes:
energy :: sustainability :: biodiversity :: tropics :: extinction :: ecosystem :: species :: global warming :: climate change ::
To provide the proper perspective for this work Svenning, who held a postdoctoral fellowship with the Smithsonian's GEO network in 2000-2002 and Condit cite empirical work by colleagues at the Smithsonian and others.
In a 2001 Science article by STRI staff scientist Carlos Jaramillo et al., plant pollen diversity in rock cores from northern South America revealed that warming events in the tropics over 60 million years were not particularly detrimental, with the caveat that warming in fragmented landscapes or crossing a temperature threshold could cause severe extinctions in the future.
Extant species that evolved in warmer climates should retain the ability to tolerate warmer climates in the future, as argued in a 2001 issue of Science by Eldredge Bermingham, director of STRI and Christopher Dick, professor of ecology and evolutionary biology at the University of Michigan at Ann Arbor.
It is not clear which factors (temperature, moisture, competition with other species, habitat limitation) are the primary causes of tropical extinctions. Drought tolerance, however, definitely limits tropical plant distributions. This was reported in the May 2007 issue of Nature by Bettina Engelbrecht, research associate and lecturer at San Francisco State University, and colleagues.
Condit and Svenning also cite their own studies from the tropics and temperate areas where other drivers of extinction are at work. They call for more discoveries of the sort that often result when researchers are brought together in places like STRI's facilities in Panama, where camaraderie fuels critical ecological research within an intellectual context that encourages a deep time and wide world perspective.
The Smithsonian Tropical Research Institute, headquartered in Panama City, Panama, is a unit of the Smithsonian Institution. The Institute furthers the understanding of tropical nature and its importance to human welfare, trains students to conduct research in the tropics and promotes conservation by increasing public awareness of the beauty and importance of tropical ecosystems.
Picture: How will a warmer world affect seasonal behavior such as the flowering of these Cuipo trees in Panama? Credit: Marcos Guerra, STRI
References:
Jens-Christian Svenning and Richard Condit, "Biodiversity in a Warmer World", Science 10 October 2008: Vol. 322. no. 5899, pp. 206 - 207, DOI: 10.1126/science.1164542
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Friday, October 10, 2008
Researchers develop tool to assess the risk of desertification
Using a general model of desertification, researchers from the Escuela Técnica Superior de Ingenieros Agrónomos of the Universidad Politécnica de Madrid managed by Javier Ibáñez have developed indicators that predict the future state of an area and hence the sustainability of current land use. This general desertification model is used as a virtual laboratory where it is possible to reproduce the different syndromes of desertification, such as overgrazing and overdrafting of aquifers.
Desertification has been described as one of the biggest environmental and socioeconomic problem faced by many countries all over the world. In arid regions, the cause of the problem is mainly the way the land is used. The definition that is most extended and that was approved by the United Nations in 1994 is that desertification is the degradation of land in arid, semi-arid, sub-humid and dry areas resulting from different factors such as climatic variations and human activities.
There are two ways to fight desertification. One of them consists in cancelling out the effects it causes, which is very expensive considering all the investments required to restore lost fertility to the soils. The other is to anticipate the problem, since during its initial stages it can still be managed and turned around. In this sense, the diverse existing methods seek to detect the early symptoms of degradation.
The traditional indicators, based on physical measurements such as plant density and erosion rates, are precise but have two serious inconveniences. Firstly, since they measure characteristics of desertification, they give information about an on going process without providing information about the long term result of such processes. The second drawback is that they often focus on very particular characteristics of the landscape, such as certain plant species, making these techniques hard to export to other territories.
The proposed tool aims to complete the information offered by the conventional indicators with simulations that would virtually reproduce the threatened environments, allowing for the development of specific indicators that would sound an alarm when critical thresholds representing long term desertification effects are reached:
energy :: sustainability :: biomass :: bioenergy :: agriculture :: land-use :: soils :: desertification :: ecology ::
In particular, the study carried out by the researchers from the UPM consists of the development of a set of generic equations that represent different desertification syndromes. The model, constructed by means of systems dynamics, links physical and socioeconomic processes. This implies that phenomenons like aquifer salinisation or soil degradation can be studied along with the benefits for the farmers and their opportunity costs.
The procedure is born with the goal of estimating the risk of desertification in any part of the world, including regions where field data is non existent and it is for this purpose that it has been designed. Up to now, it has been applied to the field of Dalías (Almería) and its system of coastal aquifers, the grazing grounds of Lagadas (Greece) or the oases at Morocco and Tunisia.
Currently this method is being used to study the erosion of the olive plantations in Andalusia and their impact of livestock in grazing lands in Senegal.
References:
Ibáñez, Javier; Martínez Valderrama, Jaime; Puigdefabregas, Juan, “Assessing desertification risk using system stability condition analysis”, Ecological Modelling 213 (2), 180-190, May 10, 2008, doi:10.1016/j.ecolmodel.2007.11.017
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