List of knowledge gaps identified from Chapter 4 on Status and trends of land degradation and restoration and associated changes

Here is a list of gaps identified on Status and trends of land degradation and restoration and associated changes in biodiversity and ecosystem functions, taken from Chapter 4 (not exhaustive):

• p. 292, l. 11188-11189: "At a regional or global scale, distinguishing the impacts of climate change and variability from anthropogenic degradation remains problematic"
• p. 294, l. 11237-11239: "Changes in species composition in rangelands to less palatable species and increases in woody plant density. These changes are often less easily detected, especially in global monitoring products, but manifest in reduced livestock carrying capacity, with up to ten-fold reduction being reported."
• p. 294-295, l. 11264-11280: "However, impacts on biodiversity from other forms of degradation are poorly resolved, especially at regional and global scales. Few accurate measurements of species numbers exist for many groups of organisms, owing to difficulties in detection. Hence, many global estimates are based on a few, easily-observed groups such as higher plants and large animals that are unlikely to be representative of actual numbers - although they do allow for processes to be tested."
• p. 303; 395, l. 11540; 14254-14261: "It is rare that the ecological processes are sufficiently well-known and can be measured to be used as baselines.  (...)  “Degradation” is a comparative term and implies a comparison with a non-degraded condition. Clearly reference conditions are integral to detection of degradation and trends. Such baselines of ecosystem extent and condition must be explicit (see Chapter 2, Section 2.2.1.1 and Section 4.1.4). Furthermore, attention is needed to the precision of both the baseline as well as the new measurements so the statistical significance of comparisons and trends can be known. This is especially important in the case of degradation that is slow and insidious, unrecognizable on an annual basis, but which can lead to total collapse over decades (e.g., declines in biodiversity, gradual invasion by aliens, changes associated with climate change), and theses can go undetected or be exaggerated without specifying statistical probability."
• p. 320, l. 11968-11970" In spite of gains in crop productivity and implementation of engineering and agronomic practices to conserve soil, the question remains: at the regional scale, are cultivated soils still losing or gaining carbon?"
• p. 345, l. 12791-12799: "Currently, unravelling the processes, consequences, severity and extent of drought versus degradation, even in the iconic and well-studied Sahel region, remains contentious. The maps that show the locations and intensity of desertification, all have serious shortcomings since they are based either on subjective assessments by experts, or on unproven methodology, and therefore cannot be applied globally nor used in future for monitoring (Gibbs & Salmon, 2015; Prince, 2016). This problem is partly because a range of distinct environmental processes are often lumped together under the term desertification, e.g., sheet erosion, productivity, loss of palatable species, bush encroachment (Nicholson, 1996; Nicholson et al., 1998; Prince, 12797 2002, 2016) and, even when a distinct process is addressed, suitable metrics can be difficult or impossible to apply spatially (Bunning, McDonagh, & Rioux, 2011), especially over large areas."
• p. 353, l. 12983-12988: "Degrading the landscape can cases thresholds to be exceeded, causing abrupt changes in landscape processes that are often irreversible and beyond which unexpected changes occur (Hanski and Ovaskainen 2000) (also see Section 4.1.2.1.) which can lead to catastrophic shifts in land cover and functions (Scheffer et al., 2001) (also see Section 4.2.6.2), however, these relationships are poorly understood. The landscape scale is a critical component of the links between local and global scales."
• p. 387, l. 14040-14042: "Besides a few local studies, mostly in the Amazon region, (e.g., Alvarez-Berríos and Mitchell Aide 2015; Swenson et al., 2011), there are no global estimates of land degradation by artisanal and small-scale mining."
• p. 392, l. 14168-14173: "Unfortunately there is a pervasive and alarming trend toward more sparse coverage and even losses of complete environmental and ecological monitoring networks, for example, more than half the global hydrological stations reporting in 1970 were not operating in 2000 (Wahl, Thomas, & Hirsch, 1995). A lack of stable, long-term commitment to observations, and lack of a clear transition plan from research to operations, are two frequent limitations in the development of adequate responses to land degradation (Hansen et al., 2013; Karl et al., 1995)."