TIER 1: Theory and Concepts
The main objective of Tier 1 is laying the conceptual foundation for interdisciplinary integration and transfer to other TP phenomena. Our research question is: “How do we develop an interdisciplinary perspective for a better conceptual understanding of socio-ecological tipping points?” – In our studies of Phase 1, we searched for non-linear responses of soil and vegetation along local grazing gradients and the relation of these ecological dynamics to social drivers. The results show a quite complex picture of strong linkages between social and ecological dynamics under the additional impact of climate forcing. This led to assumptions on interlinked social-ecological tipping point dynamics with a cascade-like behaviour. Moreover, system seem to evolve towards either desertification or woody plant encroachment. A combined conceptual consideration of these complex phenomena is challenging, as different conceptual approaches have been hardly connected so far. Therefore, WPs under Tier 1 aim to further develop the conceptual understanding of cascading DTPs, and of the alternative TP of woody plant encroachment. For example, we hypothesize that rangeland degradation in semi-arid savannas might not occur on a stability landscape with two stable states of attraction (grass-dominated or bare ground), but with three stable states, thus adding a bush encroached state.
Tier 1 (“Theory and Concepts”) includes the following WPs:
WP 1: Cascading tipping points (TP) in social-ecological systems (SES)
We assume that tipping points cascade hierarchically through system components, not only through levels of biological organization but also throughout an SES. Accordingly, the first aim of this WP is to develop a conceptual and methodological framework for investigating cascading effects in an SES’ ecological subsystem. For this, we will transfer TP phenomena recently detected along climate gradients to combined climate-grazing gradients; and develop an environmental harshness index to detect cascading effects in the ecosystem. Secondly, since DTPs interact with the social system, we will develop social indicators. Finally, we will conceptually connect cascading TP effects in an SES’ subsystems, based on empirical findings from both project phases.
WP 2: Alternative tipping points in SES under climate change
WP2 extends the understanding of cascading tipping points in rangelands to the formation of alternative tipping points. Specifically, in addition to the tipping point of grassland desertification (DTP) studied in Phase 1, the degradation process of woody plant encroachment is considered as an additional, alternative TP. The investigation of the encroachment tipping point will be done mostly conceptually. We will focus in particular on the ecological dynamics, but also address the social aspects promoting one or the other trajectory. The overarching goal is to provide other WPs with an alternative scenario for tipping point dynamics and possible alternative interventions.