There is increasing international momentum to support more sustainable land management, driven by strong global acknowledgement that land degradation can have negative impacts for both climate change and biodiversity (Reed and Stringer 2015). As a result, the concept of Land Degradation Neutrality (LDN) has been formally introduced in global sustainability planning enshrined in the Sustainable Development Goals (SDG target 15.3). LDN refers to a state of zero net land degradation, where ‘the amount and quality of land resources necessary to support ecosystem functions and services and enhance food security remain stable or increase within specified temporal and spatial scales and ecosystems’ (UNCCD 2016). LDN therefore balances degradation with maintenance and improvement of the land’s condition through restoration and sustainable land management (SLM) practices, on- or off-site (Barkemeyer et al. 2015). Restoration implies an ecosystem’s return from a degraded to a functional state, while SLM practices aim to prevent the loss of ecosystem functioning and even further improve an ecosystem’s functionality. SLM increases an ecosystem’s resilience defined as the degree of disturbance it can withstand while remaining within critical thresholds, thus maintaining its core structure and functioning (Holling 1973).

How LDN can be operationalised is currently considered in the work programme of the United Nations Convention to Combat Desertification (UNCCD)’s Science-Policy Interface (SPI) (Orr et al. 2017). The SPI recognises that while LDN is an international policy target, aggregate efforts at smaller scales enable progress. Indeed, countries at the 2015 UNCCD Conference of the Parties agreed to set voluntary LDN targets, acknowledging that ‘striving to achieve SDG target 15.3 is a strong vehicle for driving the implementation of the UNCCD’ (UNCCD 2015; Decision 3). National level target-setting means that decisions will be needed on where and when best to invest in sustainable land management (SLM) and restoration, depending on the types and status of land degradation in each country. This presents a need for cost-effective decision making and a deeper understanding of the costs of inaction as well as the costs of different types of action.

The recent Economics of Land Degradation (ELD) Initiative report ‘The Value of Land’ provided a new evidence base that partly addresses this need (ELD 2015). The ELD report has helped policymakers to better appreciate that globally, misuse of vegetation, soils and water has undermined the land’s capacity to maintain healthy ecosystems and to provide important ecosystem services, and that this bears a significant cost (ELD 2015). However, land degradation cannot be easily decreased everywhere at acceptable cost: location-specific factors determine costs and success. It requires local socio-ecological causal factors and their interlinkages with broader contextual conditions to be well-understood for interventions to be effective (Suding 2011, Wilson et al. 2011, Diffenbaugh and Field 2013). Moreover, land degradation and climate change are closely linked phenomena. Widespread land degradation is both a driver and consequence of climate change (Reed and Stringer 2016). Degradation can cause stored carbon to be released while also reducing adaptation options and biodiversity. Higher atmospheric greenhouse gas concentrations will increase future climate variability, including more extreme droughts and peak rainfall, potentially driving even more severe degradation and limiting adaptation even further.

While existing scientific knowledge and practical implementation skills can clearly support sustainable land management decisions (Chasek et al. 2015, Stavi and Lal 2015), decision makers lack evidence that can guide them on where and when best to invest in restoration and SLM. In particular, decision-making requires an understanding of key non-linear ecosystem dynamics including critical thresholds, which ecosystems often, but not always, exhibit (Suding and Hobbs 2009). The CASCADE project has as a core objective to improve our understanding and thereby our ability to predict and prevent dryland degradation, and in particular catastrophic shifts, i.e. abrupt, unexpected and often irreversible degradation of dryland ecosystems. Through multi-faceted research activities including fieldwork, ecological modelling and economic appraisal of available management options, data and tools are produced to support management. By applying principles from ecological theory of non-linear ecosystem dynamics, it is possible to inform appropriate investments in recovering and sustaining ecosystems. It is therefore vital that approaches are identified that bring together these concerns to inform sustainable land management decisions and long-term cost-effective and efficient progress towards LDN.

In this section of CASCADiS, we demonstrate the utility of considering non-linear ecosystem dynamics to provide essential insights into appropriate timings, climate-induced windows of opportunities and risks and the financial viability of land management investments. Using this conceptualisation, we outline a modelling strategy to evaluate the socio-ecological effectiveness of land management defined here as the potential of a management strategy to help maintain or restore ecosystem services while ensuring land users meet their basic needs. In linking non-linear ecosystem behaviour to an economic evaluation of land management options, we identify opportunities and challenges for cost-efficiently moving towards the LDN target.

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