Highlights
•Land Degradation Neutrality is conceptualized as equilibrium in land systems.
•Measuring Land Degradation Neutrality requires indicators of the balance.
•Conceptual graphs for different land degradation status are proposed.
•Methods to quantify the balance of ecosystems' qualities and services need research.

Abstract
The paper explores the background and scientific basis of Land Degradation Neutrality (LDN), a new paradigm reflecting the inter-related aspirations and demands of land-related sustainable development goals. The paper draws on academic literature, field observations, insight from development researchers and practitioners, professional meetings, and agency reports to describe the LDN concept and its relationship with sustainable land management (SLM). We discuss the potential for LDN to facilitate the adoption and assessment of SLM, and to provide a framework to achieve the “land degradation neutral world” goal of the Sustainable Development Agenda 2030. We present insights relevant to the implementation of LDN. These include the need to: consider quality as well as quantity of land degraded and restored; apply an ecosystem-based approach for LDN assessment; consider land degradation risks; recognize different uses of land and approaches to reach the LDN target; and define the LDN baseline and indicators. We discuss the contradictions of using two different modes for evaluating land degradation and successes in land restoration, which we name the “Anti-degradation view” and “Production-advocacy view”. To harmonize these approaches we propose that LDN be considered as a phenomenon of equilibrium of the land system, in terms of the balance between deterioration and improvement of terrestrial ecosystems' qualities, functions and services. Indicators to reflect this balance can use different approaches relevant to the various countries and areas, and to the types of land use. Two examples of using this approach are described. The first shows the assessment of the state of LDN based on the homeostasis of land cover and is based on assessment of distribution of ecosystems, and the dynamics of the land cover pattern in the areas prone to land degradation. The second is based on the combination of the well-known principle of Leibig's Law of the Minimum (1843), and Shelford's Law of Tolerance (1911), and focuses on the balance of the components as the major determinant of a sustainable system. Both approaches are illustrated using schematic diagrams to represent different balanced or destabilized situations. We conclude that the comprehensive assessment of the components of land systems and their mutual equilibrium, which determine the potential for sustainable functioning, therefore can be a basis for the development and selection of the most appropriate indicators and measures of LDN at global, regional and local levels, and that LDN could serve as a target and indicator of SLM. Nevertheless, LDN as a phenomenon of equilibrium of the land system needs further scientific research, and development of effective methods to measure the balance between different terrestrial ecosystems' qualities, functions and services.