Category Archives: Ecological Management

The Greening of Sahel: Passive recovery or active adaptation?

The drought years in the Sahel in the early 1970’s that resulted in a large-scale famine gave rise to scientific and policy discussions about land degradation and desertification. A popular belief was that the limited resource base in the Sahel, with vulnerable soils and highly variable and scarce rainfall could not sustain the growing population. The droughts was seen as a stress to a system which was already struggling with a rapidly decreasing resource base (e.g. deforestation of woodlands for agricultural expansion, shortening of fallow times, and soil nutrient depletion) and bad land management practices leading to increased poverty and out-migration.

Sahel Greening.  Overall trends in vegetation greenness throughout the period 1982–2003 based on monthly AVHRR NDVI time series. Percentages express changes in average NDVI between 1982 and 2003. From Hermann et al 2005

New analysis of satellite data, by among others Olsson et al., illustrating a greening trend in the Sahel since 1983 thus comes as a surprise for many people. It has also triggered a scientific discussion of whether this greening is merely a recovery of vegetation due to increasing rainfall, or if this trend at least partially can be explained by widespread changes in land management by farmers in the region. Hutchins et al., in the introduction to a recent special issue of Journal of Arid Environments, suggests that there is increasing evidence that farmers have adapted to the changes during the droughts and made a transition from degrading land use trajectories to more sustainable and productive production systems, suggesting that the recovery in many places actually is an active adaptation by the farmers in the region.

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Global Consequences of Land Use

Growing world population and increasing wealth are driving demands for more food production. Croplands and pastures occupies today roughly 40% of the land surface and global land cover and is according to the Millennium Ecosystem Assessment (MA) the main modification humanity makes to land cover, and therefore a main driver of ecological change, and biodiversity loss at the global scale.

In a new paper in Science, Jonathan Foley et al. reviews the Global Consequences of Land Use , and discuss consequences of land use on food production, water resources, forests, regional climate and air quality and infectious diseases. They highlight the challenge of managing trade-offs between immediate human needs and maintaining the capacity of the biosphere to provide goods and services in the long term.

Current trends in land use allow humans to appropriate an ever-larger fraction of the biosphere’s goods and services while simultaneously diminishing the capacity of global ecosystems to sustain food production, maintain freshwater and forest resources, regulate climate and air quality, and mediate infectious diseases…

…The conclusion is clear: Modern landuse practices, while increasing the short-term supplies of material goods, may undermine many ecosystem services in the long run, even on regional and global scales. Confronting the global environmental challenges of land use will require assessing and managing inherent trade-offs between meeting immediate human needs and maintaining the capacity of ecosystems to provide goods and services in the future. Assessments of trade-offs must recognize that land use provides crucial social and economic benefits, even while leading to possible longterm declines in human welfare through altered ecosystem functioning.

…Society faces the challenge of developing strategies that reduce the negative environmental impacts of land use across multiple services and scales while maintaining social and economic benefits.

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Pleistocene Park: using grazing to produce a regime shift

Sergey A. Zimov has an article in the 6 May 2005 Science about his efforts to create a Pleistocene Park where recreated Pleistocene grazing will flip from a moss dominated system to grassland. Its a great example of a large scale attempt to flip a system from one alternative state to another.

Zimov writes:

This view means that the present Holocene climate of northern Siberia, particularly near the present tree line, is likely just now to be optimal for the mammoth ecosystem. If we accept the argument that the pasture landscapes were destroyed because herbivore populations were decimated by human hunting, then it stands to reason that those landscapes can be reconstituted by the judicious return of appropriate herbivore communities.

In northern Siberia, mainly in the Republic of Yakutia, plains that once were covered by tens of meters of mammoth steppe soils now occupy a million square kilometers. The climate of the territory is near optimal for northern grassland ecosystems. Thus, in principle, the ancient mammoth ecosystem could be restored there.

In Yakutia, we are trying to do just that. The government has adopted a program to restore the republic’s former biodiversity. One thrust of this effort has been through the nonprofit organization of Pleistocene Park–of which I am a founding member–on 160 km2 of Kolyma lowland. One-third of the territory is meadow, one-third is forest, and one-third is willow shrubland. Today, many of the animals of the mammoth ecosystem and grasses remain in northern Yakutia.

Reindeer, moose, Yakutian horses, recently reintroduced musk oxen, hares, marmots, and ground squirrels forage for vegetation, and predators, including wolves, bears, lynxes, wolverines, foxes, polar foxes, and sables, prey on the herbivores. However, strong hunting pressure has kept the overall number of animals low. Therefore, their influence on vegetation is small. The first step for Pleistocene Park, which we are just now initiating, is to gather the surviving megafauna of the mammoth ecosystem (initially without predators) within the part of the parkland that is rich in grassland. The second step will be to increase the herbivore density sufficiently to influence the vegetation and soil. As animal densities increase, the fenced boundary will be expanded.

The most important phase of the program will be the reintroduction of bison from Canada and subsequently, when the herbivores are sufficiently abundant, the acclimatization of Siberian tigers. In many regions of the Amur River basin, where this formidable predator survives, January temperature is as low as -25º to -30ºC. The tigers’ survival there is limited more by poaching and herbivore density than by climate. Scientifically, Pleistocene Park is important because it directly tests the role of large herbivores in creating and maintaining grassland ecosystems, something that can only be surmised but not proven from the paleorecord.

Science 282, 31-34 (1998)] also had a news story by R. Stone about the start of Zimov’s ambitious Pleistocene Park project: A Bold Plan to Re-Create a Long-Lost Siberian Ecosystem

Ecological Basis for Managing Ecosystem Services

Claire Kremen has a article Managing ecosystem services: what do we need to know about their ecology? in Ecology Letters (Volume 8 Issue 5 Page 468 – May 2005).


Human domination of the biosphere has greatly altered ecosystems, often overwhelming their capacity to provide ecosystem services critical to our survival. Yet ecological understanding of ecosystem services is quite limited. Previous work maps the supply and demand for services, assesses threats to them, and estimates economic values, but does not measure the underlying role of biodiversity in providing services. In contrast, experimental studies of biodiversity-function examine communities whose structures often differ markedly from those providing services in real landscapes. A bridge is needed between these two approaches. To develop this research agenda, I discuss critical questions and key approaches in four areas: (1) identifying the important ‘ecosystem service providers’; (2) determining the various aspects of community structure that influence function in real landscapes, especially compensatory community responses that stabilize function, or non-random extinction sequences that rapidly erode it; (3) assessing key environmental factors influencing provision of services, and (4) measuring the spatio-temporal scale over which providers and services operate. I show how this research agenda can assist in developing environmental policy and natural resource management plans.

Ecology needs more thinking like this paper if we need to develop our understanding of how to manage ecosystem services.

Environmental Economics and the Economist

The Economist has a long article on the importance of and advances in ecological valuation. They seem to have become fans of the work of the MA.

The article begins with an interesting example of the establishment of a market for ecosystem services associated with the Panama Canal:

AT the Miraflores lock on the Panama Canal it is possible to watch the heartbeat of international trade in action. One by one, giant ships piled high with multi-coloured containers creep through the lock’s narrow confines and are disgorged neatly on the other side. If it were not for the canal, these ships would have to make a two-to-three-week detour around South America. That would have a significant effect on the price of goods around much of the world. It is therefore sobering to consider that each ship requires 200m litres of fresh water to operate the locks of the canal and that, over the years, this water has been drying up.

Scientists at the Smithsonian Tropical Research Institute, in Panama, think that reforesting the canal’s denuded watershed would help regulate the supply. One of them, Robert Stallard, a hydrologist and biogeochemist who also works for the United States Geological Survey in Boulder, Colorado, has operated in the country for two decades, and knows the terrain well. A deforested, grass-covered watershed would release far more water in total than a forested one, he admits, but that water would arrive in useless surges rather than as a useful steady stream. A forested watershed makes a lot more sense.

Another problem caused by deforestation is that it allows more sediment and nutrients to flow into the canal. Sediment clogs the channel directly. Nutrients do so indirectly, by stimulating the growth of waterweeds. Both phenomena require regular, and expensive, dredging. More trees would ameliorate these difficulties, trapping sediments and nutrients as well as regulating the supply of fresh water. Planting forests around the Panama Canal would thus have the same effect as building vast reservoirs and filtration beds.

Viewed this way, any scheme to reforest the canal’s watershed is, in fact, an investment in infrastructure. Normally, this would be provided by the owner. But in this case the owner is the Panamanian government, and Panama is in debt, has a poor credit rating and finds it expensive to borrow money. And yet investing in the canal’s watershed clearly makes economic sense. Who will pay?

In the case of the Panama Canal, the answer may turn out to be John Forgach, an entrepreneur, banker and chairman of ForestRe, a forestry insurance company based in London. Mr Forgach’s plan is to use the financial markets to arrange for companies dependent on the canal to pay for the reforestation. Working in collaboration with several as-yet-unnamed insurance and reinsurance companies, Mr Forgach is trying to put together a deal in which these companies would underwrite a 25-year bond that would pay for the forest to be replanted. The companies would then ask those of their big clients who use the canal to buy the bond. Firms such as Wal-Mart, and a number of Asian carmakers, which currently insure against the huge losses they would suffer if the canal were closed, would pay a reduced premium if they bought forest bonds.

And then moves on to discuss a bit of the scientific background:

science is producing abundant evidence that the natural environment provides a wide range of economic benefits beyond the obvious ones of timber and fish. Ecologists now know a great deal more than they used to about how ecosystems work, which habitats deliver which services, and in what quantity those services are supplied. Last month, for example, saw the publication of the Millennium Ecosystem Assessment, the first global survey of ecological services. Its authors warn that attention will have to be paid to these services if global development goals are to be met.

But the only way this can happen is if ecological services have sound, real (and realistic) values attached to them. As Valuing Ecosystem Services, a report written recently for America’s National Research Council, points out, the difficult part is providing a precise description of the links between the structures and functions of various bits of the environment, so that proper values can be calculated. What this means is that the more there is known about the ecology of, say, a forest, the better the valuation of the services it provides will be. Fortunately, according to two reports published by the World Bank (pdf ) at the end of 2004, significant progress has been made towards developing techniques for valuing environmental costs and benefits. There is, says one of these reports, no longer any excuse for considering them unquantifiable.

The valuation of ecosystem services is not without its difficulties. Nevertheless, the fact that there is a growing consensus about how and where it is appropriate is an important step forward for economists and environmentalists. In 1817, David Ricardo, a pioneering economist, noted that abundance in nature was rarely rewarded: “where she is munificently beneficent she always works gratis.” But if nature pays, who then will pay for nature?

Governing the Resilience of Venice

Venice lies in the shallow waters of a coastal lagoon connected to the northern tip of the Adriatic sea. It is occupied for more than 1500 years, and in the 14th century it became a major martime power. However, human activities have reduced the resilience of Venice which is increasingly experiencing floodings. The buffering capacity of the lagoon has been reduced by pollution (affecting sea weed vegetation which keep sand together), fishery (clam fishing by mechanical equipment that damage the lagoon bed), groundwater withdrawn and sealevel rise (climatic change). Venice in Peril is a committee that coordinates research to save Venice. A nice book came out on this subject “The Science of Saving Venice” which can be ordered from this website.
A flooded St Mark's Piazzetta

Resilience of Great Barrier Reef

On March 10th, the Christian Science Monitor an article on Terry Hughes work on the Great Barrier Reef in Australia. In particular how its management is being changed by resilience ideas.

In the past, researchers would study tropical-reef response to single events – such as a hurricane, tropical cyclone, or coral bleaching – to evaluate its ability to bounce back.

“People wrote about these as one-off events,” explains Dr. Hughes, a professor at James Cook University in Townsville. “But on longer time frames – from decades to centuries – those are recurrent events. We’re now asking: How can this system, on a scale of thousands of kilometers, absorb recurring disturbances without going belly-up? Resilience is about the system absorbing changes” and conservation managers “being proactive in anticipating them.”

Scott Wooldridge is developing a “state of the reef” computer model at AIMS that will allow conservation managers to rank the resilience potential for different reefs or reef segments. The model has the potential for use worldwide. So far, he’s included three elements: adequate levels of grazing fish on the reef to keep algae at bay, water quality, and increased heat- tolerance among coral – which he acknowledges is the weakest link in the chain in terms of biological research.

The model points to some disturbing results. Australia – and specifically, the Great Barrier Reef Marine Park Authority – may have chosen the wrong approach when it set up its no-take areas, he says.

His preliminary results suggest that the northern third of the reef probably should get the most conservation attention. The park agency, by contrast, set aside ecologically representative areas scattered throughout the reef. That made sense at the time, Dr. Wooldridge says, given what scientists then knew. But the northern segment is more pristine and faces fewer stresses because fewer people live and visit there. While it will likely feel the bleaching effects of climate change more strongly at first than reef sections farther south, it still stands a good chance of surviving. Thus it will be able to provide the larvae that will ride prevailing currents south to reseed portions of the reef that are under greater multiple stresses.

It’s a controversial notion, Wooldridge acknowledges, and calls into question the strategy over which the government spent so much time and political capital.

“With proper management, you can still have a viable reef by 2050,” he says. “But the implications are that we need to conserve more in the north.”