INSERT TABLE 3 HERE
In this review, we illustrate the natural and anthropogenic factors that affect desertification are the parched climatic condition and mis- land-use planning respectively. The dominant factors have been assessed for six countries, including China, Kuwait, Turkey, United Arab Emirates, Sri Lanka and Pakistan. In five out of these six countries (i.e. China, Kuwait, Turkey, Sri Lanka, Pakistan), desertification was thought to be principally triggered and accelerated by anthropogenic factors that included unsustainable land use, population growth, and socio-economic development. Whilst, desertification in the United Arab Emirates was primarily triggered by the natural factor (i.e. wind erosion). Anthropogenic (human-induced) activities taking up a crucial role of desertification in the BRI countries, while natural factors become dominated in some dryness and half dryness regions. Still, the dominance of natural and anthropogenic factors has yet been assessed in many BRI countries.
In addition, previous studies on desertification focused on investigating the impact of natural factors (e.g. climate change, temperature, wind pattern, etc.) or solely focusing on anthropogenic factors (e.g. land-use changes, human-induced de-vegetation, new developments, etc.). Few studies have simultaneously addressed the combined factors on natural and human activities and their interactions (Feng et al., 2015, Xu et al., 2019a). Relative contribution on the combined effect by natural (i.e. climatic change) and anthropogenic factors influencing desertification is still vague across the BRI countries. This constrains on the perception and understanding of current fundamental mechanisms of desertification processes; and thus limits the capacity of predicting future desertification pattern.
Furthermore, this also influences the development of an assessment system for desertification accordingly, such as establishing applicable criteria and parameters of control measures (e.g. surface area and expansion of desertification, drought, vegetation coverage, rainfall, etc.). That leads to the misunderstanding of desertification status by flawed perception and mis-interpretation on desertification, and eventually causing the development and implementation of ineffective desertification control measures and strategies (Wang et al., 2008). Recently, Feng et al. (2015) developed the quantitative approach that illustrated “a pooled regression model ” to estimate the combined effect from natural (climate change) and anthropogenic (human-induced) factors on desertification in China between 1983 and 2012, while Xu et al. (2019) assessed the relative role of climate change and human activities in desertification of North China between 1981 and 2010. Feng et al. (2015) found that actually the human-induced (i.e. socio-economic) factor is the most influential driver for desertification, accounting for 79.3% among all factors and drivers, while Xu et al. (2019a) demonstrated that the climate change (12.6%) was more important than human interventions (7.2%) in desertification expansion. The difference in the findings of the above two research could be attributed to the difference in the geographical domain of their study areas (i.e. the whole of China VS North China). However, similar studies should be encouraged to be promoted further in nearly future that will improve the understanding about the factors and control of desertification over wider areas of the BRI region.

5. Desertification mitigation and evaluation - the way forward

5.1 Desertification mitigation

The UNCCD is an important platform for desertification control. Whilst, the National Action Plans (NAPs) are crucial for the operation. Almost all the BRI countries have signed the UNCCD and worked out the NAPs. For example, Iran has established a National plan to control desertification in 2004 that heavily emphasise and promote the community participation (Amiraslani and Dragovich, 2011). In 2002, China enacted the “Law of Combating Desertification ”, and afterwards in 2005, enacted the “National Plan for Combating Desertification ” (Wang et al., 2013). However, many BRI countries are currently still lacking actual desertification mitigation/conservation programmes, although they have ratified the UNCCD and worked out the NAPs. Several countries that includes China, Mongolia, Myanmar, Pakistan and Hungary have launched a series of key desertification mitigation programmes (Table 4). For example, the “Three-North Shelterbelt ” project (Li et al., 2012), the project is particularly looking after the source and treatment of sandstorms across NW, N and NE China (Zeng et al., 2014). Other projects in China for desertificatoin mitigation inlcude the “Grain-for-Green project ” (1999-present), Beijing and Tianjin’s “Sandstorm Sucre Treatment Project ” (2001-2010), “Returning Farmlands to Forest Project ” (2003-present), “Returning Grazing Land to Grassland project ” (2003-present) (Feng et al., 2005). Some projects have remarkably benefited regional eco-environment (Table 4). For example, during the implementation of the “Three-North Shelterbelt Project ”, China has also revegetated a huge land area of 2.2 ×105 km2 of forests and restored 8.9 ×104 km2 of grasslands (Zhang and Huisingh, 2018).