Work package 2

Title

Historical evolution and current state of Mediterranean dryland ecosystems

 

Objectives

The overall objective of WB1 is to:

  • Define exact spatial boundaries of the ecosystems (study sites)
  • Collect data on a selection of variables
  • Quantify the relation between ecosystem change and climate and anthropogenic factors

 

Description of work and role of partners

The main objective of WB2 is to identify and trace climate and human induced drivers of change in dryland ecosystems of the Mediterranean in order to provide a basis for research in WB3 and 4. This investigation will require the establishment of a timeline where human activities and climate variations can be linked to measurable signs of degradation of semi-arid and arid environments. The WB is therefore focused on dryland ecosystems that have been irreversibly altered due to mismanagement or shifts in local management. A historical record will also be established for semi-arid and arid zones that are under pressure, in order to assist analysis in subsequent WBs. To facilitate data retrieval, these areas will have to be included in the wider regions of the selected project study areas. These primary site investigations will provide the guidelines especially for the experimental work to be carried out in WBs 3, 4 and 5. Besides information of drivers is provided to WB4 and 5, and basic data, including about historical evolution, of the sites is provided to all WBs.

 

Task 1: Definition and characterization of the case study areas

Two types of ecosystem-degradation combinations will be focused on in the study sites. The first type consists of areas where ecosystems have already committed to degradation due to anthropogenic or climatic drivers. Therefore, a review of their historical evolution can lead to evidence of instabilities and discontinuities that could reveal the actual tipping points of the ecosystem. The second type consists of areas that face a threat of change under current climatic and human activities. Task 1 will be performed by collecting and studying all available sources, such as historical hydro-meteorological datasets, publications, maps and remote sensing products. The AIU aridity index will be used in order to have initial aspect of the vulnerability of dryland ecosystems. A synoptic view about historic and present vegetation and the associated function of ecosystems can be derived from analysis of archival and on-going sequences of satellite products such as NDVI, canopy chemistry and water content. Successful estimation of these parameters can be used to study changes related to environmental stress and historical trends in for example vegetation patterns and change in land use and management practices.

 

Task2: Identification of human-induced drivers

Within selected study sites, the human induced drivers for potential ecosystem shifts will be identified. Among

them are:

  • The proliferation of livestock beyond the limitations of the ecosystem. Free-range livestock can, over time, degrade rangelands due to overgrazing. The rate of degradation depends on the density of the livestock population and the restoration rate of the natural flora. The relationship of those rates can be used as a tipping point index.
  • Overpumping that promotes salt-water intrusion into coastal groundwater and reduces water availability for plant growth, impairing primary production of irrigated croplands or deteriorating plant health in natural environments. Decrease in aquifer water levels and increase in salinization can therefore be used as early warning indicators.
  • Indirect drivers such as demographics and economics, which might cause pressures for increased productivity, potentially leading to a downward spiral of loss of ecosystem functions and services.

 

Task 3: Identification of climate induced drivers

The following climate induced drivers will be assessed and coupled to observed ecosystem changes in each of the study sites:

  • Historical temperature regimes in relation to observed ecosystem changes, accounting for effects of evaporation and soil moisture availability
  • Historical precipitation patterns in relation to observed ecosystem changes
  • Effect of carbon dioxide concentrations as important ingredient for primary production, and constituent of dryland services.
  • Effects of extreme events, like extensive and distinct droughts, wildfires a.o.

 

Task 5: Role of drivers in the evolution of ecosystems

In the final task of this WB, the drivers and the effects have to be correlated in a meaningful relationship. Special attention will be given to thresholds that once surpassed do cause direct changes. Drivers that show such "creeping" characteristics often have more devastating results than those with direct impacts.