Catastrophic shifts in drylands: How can we prevent ecosystem degradation?

It is often difficult to fully understand – much less predict – major changes or shifts in ecosystems. Nevertheless, signs of vegetation loss or soil erosion, for example, may indicate that a particular ecological threshold has almost been reached. When that threshold is crossed – producing a rapid or irreversible transition from one ecosystem state to another, with serious socioecological consequences – we speak of a "catastrophic shift".
degradation of landscapes
The degradation of landscapes often takes the form of abrupt, irreversible changes that are difficult to predict. Photo: Matteo Jucker, CDE

Guidelines for dryland ecosystem management

To obtain a better understanding of sudden shifts in drylands, the CASCADE project, funded by the EU’s FP7 programme, investigated and analysed a range of dryland ecosystems in southern Europe. CDE researchers studied land use and management practices, and the role of these practices in preventing catastrophic shifts. The research approach followed three steps:

  1. We inventoried, documented, and evaluated natural resource management practices that were already applied locally.
  2. We developed and applied a simple but effective method to assess the resilience of natural resource management practices.
  3. We prepared best-practice guidelines for natural resource managers in the following contexts:
  • Forest fire
  • Abandonment
  • Overgrazing

Each set of guidelines is available in English, Spanish, Greek, Italian, and Portuguese.

degradation forest fire
The hill in the foreground has been affected by fire. Its vegetation is recovering poorly, especially along the southwest-facing slopes. Photo: Hanspeter Liniger

Forest fire context

The results stress the importance of preventive action before a fire event. Among the land management practices that can be implemented before a fire, fuel management appeared to increase forest resilience the most. It minimizes fuel load and connectivity in order to reduce fire risk.

Management of forest regeneration (after a fire) and reforestation should promote a low-density, spatially differentiated and species-diverse canopy, which also reduces outbreaks of pests. While forest regeneration from seed banks is only possible with long time intervals between fires, regeneration from resprouting individuals fosters a quick recovery.

Guidelines for land managers: the forest fire context

Land abandonment context

In the Mediterranean, land abandonment is widespread and on the rise. The environment of abandoned land can change in unexpected and diverse ways: degraded land might not recover – or it might promote new risks such as soil erosion, flooding, or fire.

Land management options include revegetation, rotational grazing, or alternative uses of land such as beekeeping, biodiversity management, tourism, or wind/solar energy production. It should also be considered that land that is not used economically at present, can become valuable in future – and thus knowledge and infrastructure may need to be maintained. Cooperation and new forms of management (e.g. silviculture) help to overcome labour availability constraints.

Guidelines for land managers: the land abandonment context

degradation overgrazing
Overgrazing is damaging the vegetation cover, causing soils to dry out and erode. Together with their partners, CDE researchers are analysing the causes of land degradation and helping to identify appropriate land use practices. Photo: Matteo Jucker, CDE

Overgrazing context

Overgrazing reduces vegetation cover, which increases soil erosion and leads to a reduction in soil fertility, and thus productivity. CASCADE studies have shown that if surface cover falls below 30-40%, soil erosion increases sharply because of the high connectivity of bare patches.

Promising management practices to control vegetation cover include rotational grazing, fodder provision, and area closure.

Guidelines for land managers: the overgrazing context

 

To prevent sudden shifts, cost-effective management interventions that are acceptable to stakeholders should be applied before thresholds are reached. Interventions should include bundles of different practices used in combination, to mitigate the pressure and reduce vulnerability. Such interventions should also be supported by policy.

More information: http://www.cascadis-project.eu/

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The CASCADE Project is funded by the EU’s FP7 programme. It is slated to run from 2012 to 2017. Visit its site at: www.cascade-project.eu​