INSERT TABLE 1 and 2 HERE

4.2 Desertification impacts

Desertification leads to a series of socio-economic and eco-environmental issues (Bangladesh and IUCN, 2005), including lowered land productivity (Tao, 2014), reduction of soil carbon storage (Anjum et al., 2010), texture destruction (Zhang and Huisingh, 2018) and economic loss (Cheng et al., 2018). Studies have primarily foci on the influence of desertification on economic development, land productivity and regional climate condition.
In the BRI region, economic cost for desertification is large particularly when taking account of the expense for rehabilitation/desertification mitigation. In the MENA region, the annual average income loss by desertification reached at $1.98 billion. The estimated costs for rehabilitation reached $8 billion per year, which means it costs about $160 billion anti-desertification measures in the region (without considering inflation and other economic factors) for two decades (from 1970s to 1990s) (Mamdouh, 1999). Al-Saidi and AI-Juaiali (2013) found that the cost of combating desertification is around $10.3 billion (USD) to $20.5 billion (USD) in Iraq. This huge cost affects the present and future economic developments and slows down further development. Soil degradation costs around 12% of the country’s overall agronomic outputs or account for 2.5% of the “Gross National Product ” (GNP) in Syria (Haktanir et al., 2004). In China, Cheng et al. (2018) found that desertification costs at the range of 0.6% - 1.1% in the GDP through refining previous estimations. Overall, the economic cost due to desertification is lacking of consideration and assessment in the BRI countries. Even in countries experienced for desertification research (e.g. China), the economic cost of desertification has not been fully evaluated (Cheng et al., 2018).
Desertification also leads to loss of productive lands. For example in Iraq, desertification has many negative impacts and particularly leads to the degradation of productive land-use areas (Haktanir et al., 2004). Looking up north in C Asia, land degradation has decreased productivity by 30% to 40% that occurs in the highland areas of Kyrgyzstan, and decreased by 40% to 60% in Tajikistan (Gringof and Mersha, 2006). Kazakhstan’s arable land has lost up to 20% to 30% of its humus (the top soil with soil organic matter and essential for vegetation), and approximately 30% of the pastureland vegetation (6.5×105 km2) has been degraded, which largely affected the agricultural developments (Gringof and Mersha, 2006).
Desertification may affect the regional environment. The GCM modelling work conducted by Xue (1996) suggested that the desertification expanded in grasslands of Inner Mongolia and Mongolia largely affected the simulated climate through altering the water balance and surface energy balance. Wang et al. (2020) also found that desertification reversion would alter soil greenhouse gas emission in the eastern Hobg desert, China. More prominently, further land-use changes and landscape deterioration (i.e. deforestation, de-vegetation etc.) caused by rapid developments on infrastructures (e.g. building roads, transport networks, urbanisations, etc.) will exert more adverse impacts of desertification to semi-arid and arid areas and countries that are currently involved in the BRI program. For example, the effects of BRI developments may further exacerbate the dust/sand storms in the dryness and half dryness areas of C Asia and thus enhance the cumulative effects of desertification on local eco-environment and socio-economy (Indoitu et al., 2012).

4.3 Impacting factors and their relative importance

Desertification results from numerous natural and anthropogenic (human-induced) factors (EI Shaer, 2015, Feng et al., 2015, Park et al., 2018); and their interactions (Zhang et al., 2020b). Our review provided the specific drivers of desertification that have previously been investigated for 23 countries that recently joined the BRI program (Table 3).