One of the most challenging themes in ecology to date has been to understand discontinuous changes or sudden shifts in ecosystems. In the era of the 2030 Sustainable Development Goals, which encompass ideas around Land Degradation Neutrality, advancing this understanding becomes even more critical. Better identification of early warning signals for such changes can help us to develop better-timed and more cost-effective solutions, allowing anticipation of, adaptation to, or even prevention of, undesirable ecosystem shifts. The aim of the CASCADE project was to advance understanding of sudden ecosystem shifts in Mediterranean ecosystems. It takes an integrative, multidisciplinary approach to deliver conceptual, methodological and empirical advances in understanding ecosystem change.
»Research challenge and methodology
The project linked applied and theoretical ecology at multiple scales with analyses of human- environment-climate relations and stakeholder engagement in Mediterranean drylands to address three key questions:
- »What are sudden ecosystem shifts in drylands? And how do different pressures lead to such shifts?
- »What processes happen in the soil and vegetation during a shift?
- »How can we manage vulnerable ecosystems better?
In answering these questions, six »Study sites were selected in Portugal, Spain (2), Italy, Crete and Cyprus, in a West-East transect. In these study sites, various ecosystem service changes were analysed using Landscape and Function Analysis (LFA), in order to detect more subtle changes of possible upcoming ecosystem shifts, and to see which ecosystem services are decreasing and to what extent; this showed that degradation pressures severely impact ecosystem properties and services of the selected ecosystems along the Mediterranean basin in a wide range of ecological, biogeographical and historical characteristics. In field experiments, trends towards soil fertility loss with increasing fire recurrence (one, two, three or four fires in 37 years) were observed at both the short- and the long-term following fire. Labile organic matter fractions were more sensitive than total amounts to fire impact, suggesting their high indicatory value for this type of disturbance, therefore they might serve as potential early warning indicators for changes in soil functioning in response to both fire and overgrazing. Computer modelling suggests that plant patterns in a degrading landscape are also good indicators of upcoming tipping points, these conclusions are reinforced by field observations. More useful knowledge about dryland ecosystems and tipping points was discovered.
In order to prevent tipping points from taking place, cost-effective management interventions, acceptable to stakeholders, should be applied before thresholds are reached. Cooperation with local stakeholders and making use of their knowledge is vital, since they have knowledge of their land and of effective technologies. Selection of the right measures, as well as the right timing for implementation are vital for success, which implies that if the shift has already occurred, measures should be implemented during windows of opportunity when conditions are at their most favourable. Interventions should include bundles of different practices used in combination to both mitigate the pressure and reduce vulnerability, and be supported by policy.
Restoration of ecosystems that are already degraded is extremely difficult due to probable loss of mainly soil resources, but is not impossible. Successful restoration is enhanced by using multispecies in big patches, yet minimizing intraspecific competition by reducing the number of individuals per species within the same patch and combining species in the plant patches with plant traits that maximize the capture and deep infiltration of runoff water.
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