Mapping European ecosystem change types in response to land‐use change, extreme climate events, and land degradation

Abstract

Extreme climate events and nonsustainable land use are important drivers altering the functioning of European ecosystems, resulting in loss of the services provided. Yet a consensus method for regular continental scale assessment of ecosystem condition in relation to land degradation (LD) is still lacking. Here, we propose a new remote sensing‐based approach allowing for improved, repeated assessment of changing pressure on terrestrial ecosystems. On the basis of segmented trend analysis of water‐use efficiency (WUE), a map of ecosystem change type (ECT) was produced over Europe for the period 1999 to 2013. Results were related to drought and change in land use and land cover and to known cases of soil degradation (LD case‐studies). More than 30% of the European ecosystems experienced significant changes in WUE, of which more than 20% were categorized as abrupt. Large‐scale positive reversals in WUE were observed over regions with increasing crop yield and intensification of wood production, whereas decreased WUE was observed over grassland areas coinciding with high farmland abandonment. Evidence of drought pressure on ecosystem functioning (EF) was observed, with abrupt changes in functioning observed during major European drought events. The ECTs also provided relevant information on the location and type of change in EF over the LD case studies. We conclude that mapping of gradual and abrupt changes in EF is expected to be valuable tool for ecosystem condition assessment that is essential for assessing the success of reaching the LD neutrality objectives set by the United Nations Convention to Combat Desertification.

Global‐scale characterization of turning points in arid and semi‐arid ecosystem functioning

“…Such improvements represent important steps towards the comprehensive analysis of pathways of change in ecosystem functioning. For example, it was recently shown that local degradation processes (e.g., decreased vegetation productivity owing to soil erosion) would be signalled by a change in the magnitude of the slope, suggesting a slowing down in ecosystem functioning (Horion et al, 2019). Thanks to our new typology, acceleration and slowing down of ecological processes can now be captured and labelled in a systematic way.…”

“…Examples of ecological inference for the types of ecosystem changes are given in Table 1. However, it is important to note that different drivers or combinations of drivers may result in the same type of ecosystem change (Horion et al, 2019). Further research is needed to deepen our knowledge on the variability of ecosystem pathways resulting from single or combined driving forces.…”

“…The characterization of the ongoing processes in those areas (e.g., land degradation or restoration) can possibly help to set priorities when taking measures for ecosystem conservation. Although developed to characterize changes in dryland ecosystems, the new typology might also be applicable in different ecosystems worldwide, with the pre‐condition of applying it to a proxy that reflects the functioning of the ecosystem under study (Horion et al, 2019). However, adequate validation with case studies is still required to ensure the validity of the approach for other ecosystems, because the interpretation of the results might differ from those inferred from our study in dryland ecosystems.…”

“…It is therefore essential to monitor such abrupt changes. Although vegetation dynamics (e.g., changes in vegetation activity throughout time) and shifts in vegetation trends have already been addressed in global drylands (de Jong, Verbesselt, Schaepman, & de Bruin, 2012; de Jong, Verbesselt, Zeileis, & Schaepman, 2013; Fensholt et al, 2012), few studies have used an ecosystem functioning approach to do so (e.g., Horion et al, 2016, 2019; Ponce‐Campos et al, 2013).…”

“…For example, when an ecosystem is degraded and species loss happens, its productivity declines, which has severe implications for the functioning of this ecosystem and is reflected by a decrease in RUE (Chapin et al, 2000; Fensholt et al, 2013). Extreme droughts may also cause a decrease in RUE, suggesting that the ecosystem coping mechanism has reached its limit (Ponce‐Campos et al, 2013) and that the ecosystem productivity has been impacted significantly (Horion et al, 2016, 2019). The detection of major breakpoints in RUE time series indicates that the ecosystem response to precipitation has changed significantly through time and, ultimately, enables in‐depth analysis of TPs in ecosystem functioning in both anthropogenic and natural landscapes (Horion et al, 2016).…”