**1. Introduction**

China is one of the countries affected seriously by desertification [1]. China has 6.6 million km<sup>2</sup> of drylands (expanded by 8.3% during 1980–2015 [2]) that support approximately 580 million people [3]. It is in this vast territory where desertification occurs, i.e., the degradation of drylands due to climate variations and inadequate human activity [4]. Desertification affects seven main dryland provinces and autonomous regions (Xinjiang, Inner Mongolia, Tibet, Qinghai, Gansu, Ningxia and Sha'anxi) and 12 main deserts and sandy lands [1]. Although the ambiguity of this complex problem makes it difficult to assess and map [5,6], it is estimated that the direct annual economic loss caused by desertification is RMB 33.1–94.9 × 10<sup>9</sup> [7]. In addition to these effects, the irreversible nature of desertification narrows the development options of a territory [8], and poverty will be exacerbated [9].

In NW China, the most recognizable expression of desertification is serious water scarcity [10]. The increasing water gap results both from the falling supply of water, and the rising demand for water. The former is related to the effects of climate change. Climate

**Citation:** Martínez-Valderrama, J.; Gui, D.; Ahmed, Z. Oasification and Desertification under the Framework of Land Degradation Neutrality. *Environ. Sci. Proc.* **2023**, *25*, 94. https://doi.org/10.3390/ ECWS-7-14238

Academic Editor: Athanasios Loukas

Published: 16 March 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

projections in China point to a greater risk of extreme events and aridification in arid and semi-arid regions. In addition, changing snowmelt patterns [11] are a serious threat to the region's oases, which have historically depended on this water flow [12].

The latter is explained by the fast transition from food crops to cash crops. The change in land use was triggered in the early 1980s, when farmers were given more autonomy in land use [13]. In the least developed regions, farmers have few choices for increasing their income (i.e., their opportunity cost is low) besides expanding their agricultural scale [14]. Hence, this oasification process—the natural or artificial expanding the boundaries of oases—has a double edge, as it can tackle or favor desertification. Oasification leads to greater vegetation cover in places that, due to low rainfall, it is very sparse or inexistent. In addition, the quality and quantity of the soil is improved, as shown by various indicators (e.g., soil organic carbon). However, oasification can result in extensive lands being abandoned due to water shortage [15], threatening its very survival. We are, therefore, faced with an archetypal problem in drylands: it is necessary to promote economic development and try to take advantage of water resources to green the landscape, but poor managemen<sup>t</sup> of these resources can cause the whole system to collapse (i.e., lead to desertification).

This is the ambiguity of the concept of desertification, which basically stems from all that the definition of desertification [16]—recall that it is the degradation of drylands—includes in the word degradation: "the reduction or loss of the biological or economic productivity, complexity of ecosystems, and biodiversity" [4]. This controversy explains why the UNCCD has been so ineffective, and embodied the conflicting expectations of parties: developing countries regard it mainly as a development convention, while developed countries regard it as an environmental convention [17]. This dilemma is not only found in desertification, but also in the Sustainable Development Goals (SDGs), where there are important (and irresolvable) trade-offs between environmental goals (e.g., SDGs 13 or 15) and economic growth goals (e.g., SDGs 1, 2, and 8). The answer to this dilemma can be provided by Land Degradation Neutrality (LDN), with which the UNCCD could re-energize international action on desertification and regain lost protagonism [18].

LDN is defined as "a state whereby 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". LDN has been set up as the main tool to combat desertification in SDG 15.3. LDN is pragmatic because it links "development" and its implicit, associated economic benefits to restoration commitments, including offsets. It could be achieved by: (a) managing land more sustainably, which would reduce the rate of degradation; and (b) increasing the rate of restoration of degraded land, so that the two trends converge to give a zero net rate of land degradation.

This research will delve into the socio-economic drivers of oasification, where a research gap has been detected [16]. To this end, causal diagrams—one of the first stages of System Dynamics (SD) modeling [19]—will be used to understand the mechanisms underpinning oasification processes by detecting feedback loops, nonlinearities, and delays between variables. Gaining an in-depth comprehension of the functioning of the socioecosystem paves the way for proposing solutions in the framework of LDN [20].
