Restoration potential for preventing and reversing regime shifts
|Authors:||Alejandro Valdecantos (CEAM),V. Ramón Vallejo (UB), Susana Bautista (UA), Matthijs Boeschoten (UU), Michalakis Christoforou (CUT), Ioannis N. Daliakopoulos (TUC), Oscar González-Pelayo (UAVR), Lorena Guixot (UA), J. Jacob Keizer (UAVR), Ioanna Panagea (TUC), Gianni Quaranta (UNIBAS), Rosana Salvia (UNIBAS), Víctor Santana (UAVR), Dimitris Tsaltas (CUT), Ioannis K. Tsanis (TUC)|
|Source document:||Valdecantos, A. et al. (2016) Report on the restoration potential for preventing and reversing regime shifts. CASCADE Project Deliverable 5.2 104 pp|
It is already known that the higher the level of stress applied by degradation drivers (intensity, frequency, time since the last event) the lower the ability of the ecosystem to recover to the state before the disturbance and, probably, the higher the restoration effort/input to be made. However CASCADE research has shown that the ecological benefits of restoration increase almost linearly as the degradation increases until a threshold of degradation beyond which improvements in ecological services due to restoration collapse.
Ecosystem service loss and restoration potential
The intensity in time and pressure, and the frequency of the degradation drivers severely impact ecosystem properties and services moving the ecological system to states with different potentials to recover functionality and structure. In CASCADE’s field sites the loss of ecosystem services is positively related with the aridity of the site and certain degradation thresholds might have been already passed. For more details see »Structural and functional changes associated with regime shifts.
Different restoration approaches are needed depending on the degradation degree of the site, the degradation driver and the particular main objectives of restoration (such as increase diversity, reduce fire hazard, promote pastures, erosion control). However little is known about the relationship between the restoration potential and the accumulated loss of ecosystem services. For more details see »Ecosystem management for restoration.
This section of CASCADiS focuses on the assessment of some important ecosystem services in degraded and restored states of target ecosystems in all six CASCADE study sites to determine the restoration potential. We have also included data of the Reference undisturbed ecosystems as the starting point that should be desirable to achieve.
Restoration actions assessed
The restoration actions included different treatments that
- removed the burned trees early after the fire in Várzea,
- cleared selectively fire-prone shrublands combined with planting resprouter seedlings in Ayora,
- cleared undergrazed areas in Castelsaraceno,
- restricted grazing in overgrazed areas in Castelsaraceno, Randi and, combined with planting carob trees in Messara, and
- planted tree and shrub species with different ecotechnologies in Albatera.
In order to do an across-site analysis, we applied the same field methodology to evaluate five common ecosystem services in Reference, Degraded and Restored states: water and soil conservation, carbon sequestration, nutrient cycling and biodiversity. For more details see »Measurement of ecosystem properties and the potential for their restoration.
In general, and despite of the diversity of degradation drivers, reference ecosystems, restoration approaches and time since the restoration actions, we observed a positive relationship between the degree of degradation and the recovery of ecosystem services after restoration. But this positive linear trend drops sharply in the highest degraded field site, Albatera, where the restoration actions are considered as successful, our results suggest that the relationship between restoration potential and degradation level matches a non-linear model, being positive until certain threshold in the loss of services, beyond which the benefits of restoration drop sharply. From the management perspective, the implications of these results are of paramount importance for prioritizing restoration efforts and assessing the cost-benefit of restoration as a function of degradation.
For more details see »Results highlights from all study sites and »Comparison between restoration potential of study sites.
Three of the CASCADE study sites are under pressure from grazing.
In Randi and in the overgrazed state in Castelsaraceno we observed a general improvement of ecosystem properties and services by grazing exclusion, especially in Randi where plant cover, litter accumulation and aboveground biomass recovered to similar levels found in the undisturbed reference areas. As a consequence, the five ecosystem services calculated did not show differences between the restored and the reference areas and were significantly improved from the overgrazed degraded lands. In Castelsaraceno, the degradation due to overgrazing seems more severe than that due to undergrazing and biodiversity is the most improved service associated to the two restoration approaches. Fencing overgrazed areas did not achieve the overall balance of services provided by the references while in the undergrazed areas the restoration through clearing showed the highest balance of services. We discuss about the interest of defining intermediate stocking rates that might optimize ecosystem services in these grazed Mediterranean areas, including provisioning services.
Restoration in Messara aimed to transform land use from grazing to carob tree orchards as a silvopastoral or agroforestry system rather to recover the pre-disturbance state of the ecosystem. Under these circumstances, the conducted evaluation based on LFA assessment should be complemented with plant data (cover, biomass, diversity).
Two of the CASCADE study sites are under pressure from fire.
In Várzea, restoration actions improved ecosystem properties and services at the very short term (< 2 years) after their implementation although the dynamics of the plant communities were slowdown, probably due to the impact of the heavy machinery on the earliest regenerated plants. On the contrary to our expectations, traditional (salvage) logging was more effective recovering ecosystem function than the conservation logging. Nevertheless, more time is needed to assess whether the traditional and conservation logging treatments affect differently to the recovery of ecosystem properties in Várzea.
In Ayora, the assessment was conducted more than ten years after the application of restoration actions and they had positive impacts on most ecosystem properties and services, especially on biodiversity and fire risk reduction. Only C sequestration was negatively affected by restoration as actions included the removal of seeder fire-prone vegetation and hence the aboveground biomass. The reduction of fire hazard, together with increasing the resilience of the plant community, was the main objective of the restoration carried out.
The final study site is under multiple, diffuse pressures
In Albatera, the two restoration approaches based on planting conifers on terraces (traditional) and on the implementation of different ecotechnologies (water harvesting, compost addition) in multispecific plantations improved most ecosystem services in relation to the degraded areas, especially the ecotechnological restoration approach. However, the extremely harsh conditions in Albatera (highest aridity index) determined low recovery rates of ecosystem structure and function after restoration and it is expected that the positive effects of this management option will increase over time as ecological processes act at slow rate in these extremely stressed sites.