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4. Facts and implications (Spatiotemporal pattern and socio-economic changes) of Desertification

4.1 Desertification facts

Most of the BRI countries are landlocked countries with large-scale agricultural production (NRSCC, 2017) that exacerbates the degree of desertification. Thus, the desertification is widespread in the BRI region. Nevertheless, some driving factors of desertification (e.g. climate condition and human interventions) are not the same across different BRI countries, which indicate that the desertification situation in different areas have specific characteristics (NRSCC, 2019).
In East-Asian region, China and Mongolia both have been suffering from desertification seriously. Ninety percent of the Mongolian territory is vulnerable to desertification and around eighty percent of the land-use areas have already been desertified (Asigang, 2017), although some land restoration has been implemented in NW and NE Mongolia (Wang et al., 2020). These land-use areas are mainly used and operated as the rangelands (grazing areas) for supporting about 3.0 × 107 heads of livestock and numerous populations of wild animals. In China, desertification land surface areas expanded dramatically from 1.37 × 105 km2 to 3.85 × 105 km2 between 1950s and 2000 (Zhang and Huisingh, 2018), when the desertification was primarily found in steppe areas and the fringe area of deserts (Wang et al., 2002). During the decade of 2000 to 2010, total desertification region in China decreased by 1.37 × 103 km2(Zhang and Huisingh, 2018, Tao, 2014). Desertification is severely widespread in N China. In the 1980s, the area of desertification-prone land area was about 3.34 × 105 km2, and about 1.76 × 105 km2 was desertified (Zhu et al., 1988, Xue, 1996). Recently, desertification and its mitigation were found over a 7.50 × 105km2 of land in N China, and subject to a heterogeneous spatial pattern (Xu et al., 2019a). During 2011–2030, the desertification risk in N China was found by Xu et al. (2019b) to decrease under RCP4.5 and RCP8.5 scenarios. However, some regions, e.g., Turpan Hami basin and Zhungeer basin, become more sensitive to desertification.
Countries in SE Asia (such as the ASEAN countries) are normally not geographically categorised as arid or semi-arid countries (Figure 1). Even though some regions/countries, such as Vietnam and Thailand, are still at a risk of desertification resulting from prolonged droughts (Anh et al., 2006, Sok et al., 2017, Hien et al., 2019). For example, in Vietnam, forty-five percent of agricultural land has been affected by droughts, and 30% of them have been severely degraded (Hai et al., 2013). Overall, the country has over 9.0 × 104km2 of barren area, covering 28 % of the country’s total land area, of which 7.5 × 104km2 has been affected directly by desertification (Yan, 2015, Anh et al., 2006). In Thailand, the Pa Deng sub-district and the Huay Sai district are two of desertification-prone areas. Over 10% of the former was found to be subject to different levels of desertification (low level, moderate level, and high level were 2.0%, 9.1% and 0.8% of the total area, respectively) (Wijitkosum et al., 2013). In the latter, most areas (74.4%) were subject to high desertification risk in 1990s, and the risk was still high (77.2%) in 2010s (Wijitkosum, 2016).
Desertification is also widely distributed in West Asia. Dregne (1992), Mamdouh et al. (1999) assessed the desertification for the “Middle East and North Africa ” (MENA) region (including countries located in Sahara Desert), through refining Dregne (1992)’s assessment for desertification in irrigated areas (“slightly/not desertified” was changed to “not desertified”) and rangelands (the desertified area was adjusted from 80% to 50%). They found that in the MENA region 73% of rain fed croplands and 50% of rangeland were subject to different levels of desertification. In the Arabian Gulf, desertification affected 9.76 × 106km2, representing 68% of the total area in the Gulf, which threatened vastly at about 2.87 × 106km2 area (EI Shaer, 2015). Although the size of threatened or desertified areas varies among countries, Qatar, Bahrain, Kuwait and the UAE are countries mostly suffered by desertification in the region (EI Shaer, 2015).
Desertification in some of the W Asian countries has been previously investigated such as Bahrain, Turkey, Iraq, Oman, Kuwait and Syria. In Bahrain, most of the territory has been found to be at risk of desertification (Thomas and Middleton, 1994), and the aridification is likely to intensify and spread under contemporary climate conditions (Elagib and Abdu, 1997). In Turkey, approximately 3.7 × 105 km2 are prone to desertification and des-habitation (Haktanir et al., 2004), given that over 60% of the country’s territory is located in complete dryness (arid) or half dryness (semi-arid) areas. The desertification is potentially accelerated in the future under the hotter and drier climatic condition that has been projected in Turkey (Bayram and Öztürk, 2014). Across Iran, dryland accounts for over 85% of land area, and desertified and desert lands cover 3.4×104 km2(Pakparvar, 1998). Very severe, severe and moderate desertification account for 12%, 81% and 7% of the desertified area respectively (Sepehr et al., 2007). Besides Iran in the Arabian Gulf, over 92% of Iraq’s land area has been subject to desertification (Haktanir et al., 2004), which is particularly prevalent in arable areas (Al-Saidi and Al-Juaiali, 2013). The desertified area has expanded since 1981, particularly since soil, vegetation and eco-environment have been largely damaged by military operations. Down to the gateway (Oman) of the Arabian Gulf, over 95% of surface land area is considered as the “true desert ” or “moderately affected by desertification ” (Al-Balooshi and Charabi, 2012). Similar situation also occurred in Kuwait, where very severe desertification prevails, and mean annual desertified land was 285 km2 during middle 1970s-middle 1990s (Al-Awadhi et al., 2003). Desertification caused major constraints on the development in Syria, such as affected Badia Rangelands (Steppe zone), marginal regions, and the agricultural lands, largely limiting the agricultural production (Haktanir et al., 2004).
Whilst, desertification has also been found in S Asia (e.g. Afghanistan, Bangladesh, India, Pakistan, Sri Lanka and Nepal). Most of the climate models projected a dry-season precipitation decline and a monsoon precipitation increase in Southern Asia (Kripalani et al., 2007), which implies higher land desertification risk in the future. We found that around 75% of Afghanistan’s area is vulnerable to desertification (Ahmadzai et al., 2008). In India, the total land area suffered by desertification is about 8.15×105km2, including 2.62×105km2 caused by water erosion, 1.78×105 km2 by wind erosion, 1.76×105 km2 of degradation towards vegetation areas, and 9.47×105 km2of frost shattering (Ajai et al., 2009). Besides, around 90% of Pakistan’s territory falls into dryness (arid) and half dryness (semi-arid) climate, and is subject to high or severe desertification risk (Anjum et al., 2010). Thus, out of 7.96×105km2 of the country’s land area, 6.24×105 km2 are susceptible to desertification, only 4.2% land areas are covered by forests (Hussain and Irfan, 2012). In the NE Himalayan region such as Nepal, around 100 km2 in Dopla and Mustang districts (highlands areas in W Nepal) feature a process of desertification (Paudel et al., 2009).
In C Asia, desertification is one of the major threats to the ecosystem for countries including Kazakhstan, Uzbekistan, Turkmenistan and Tajikistan (Jiang et al., 2019a, Jiang et al., 2019b). In Kazakhstan, over 75 % surface land-use areas suffered from land degradation and desertification; more than 14 % of pastures have been extremely or completely degraded (Issanova et al., 2014). Land degradation and desertification areas are mainly concentrated in ecologically fragile areas, for example in the areas besides the Aral and Caspian Sea and the Lake Balhash (Almaganbetov and Grigoruk, 2008). Sixty percent of the Uzbekistan’s territory has experienced different levels of desertification (Behnke, 2008), of which the majority is potentially induced by human activities (Gringof and Mersha, 2006). In Turkmenistan, 66.5 % of the territory has been subject to human-induced desertification (Gringof and Mersha, 2006), and the irrigated land is particularly under an unsatisfactory condition due to salinization (Behnke, 2008). Over 97% of Tajikistan’s territory is subject to soil degradation, which mainly occurred in the form of soil erosion (Behnke, 2008). Besides, a modelling work, under the IPCC RCP 8.5 scenario has found that Middle and N Central Asia and NW China (besides Xinjiang, Inner Mongolia Provinces) are likely to experience an accelerated desertification (Miao et al., 2015).
Across Siberia, the BRI corridors (i.e. ELBEC and CMREC) cover the large areas between the Russia and surrounding countries. Desertification was mainly reported in Russia, Armenia and Georgia around the Black Sea. In Russia, the land-use area that is experiencing desertification reach at 1.25 × 106 km2 (Kust et al., 2011). In Armenia, about 2.4 × 104 km2 or 81.9% of the territory is subject to desertification. The severely, strongly, moderately and poorly affected territories cover 26.8% 26.4%, 19.8% 8.8% of the territory respectively (Yerevan, 2002, Susanne Khachatryan, 2013). In Georgia, the south-eastern part of the country is sensitive to desertification, where the catastrophic development of desertification processes begins, as precipitation is less than 200 mm (Davitashvili et al., 2009).
Looking further to Europe, approximately 10% of the total surface land areas are affected by the desertification processes (Rubio et al., 1998). The Mediterranean and Eastern European regions are especially threatened by desertification owing to natural and socio-economic factors (Rubio et al., 1998). We found that 20 European Union (EU) member states declared as countries affected by desertification under the “United Nation Convention on Combating Desertification ” (UNCCD) in 1992. For examples, EU member states countries located in the C and E Europe; they have been declared and engaged in the UNCCD. In Romania, forty-eight percent of the country’s agricultural land (7.1 × 104 km2) was affected by drought (Lupu et al., 2010). In S, SE and E Romania, these regions belong to the most severe drought areas during the 2000s (Mateescu et al., 2013). In Cyprus, similarly, some areas prone to desertification is likely to increase from 57% to 70.4% in 2050s under the projection of climate change (ClimateChangePost, 2018). In the C Hungary, the central part of the country is the most sensitive area to desertification because of severe drought and the desertification risk is likely to be enhanced by climate change (Kertész, 2016).
Whilst, most of the BRI countries have declared the development of desertification, the exact desertification area is still only available for 18 (out of the 66) BRI countries in terms of our review (Tables 1 and 2). Given the spatial area and distribution of desertification is crucial for designing and implementing the strategies on controlling desertification, quantitative evaluation of desertification is urgently required for the BRI countries. Moreover, the desertified area for most of these 18 countries was a rough number that is not clearly associated with a specific period (Table 1). That implies that the area of desertified land for these countries was evaluated at a low accuracy and not regularly updated, limiting the analysis of active changes in desertified land areas. The mechanism of monitoring on the level of desertification, and understanding the spatial size of desertification (measured by surface area that suffers from desertification) are therefore essential for the BRI countries in terms of investigating the causes and solutions of desertification. That also addresses some important issues, such as validation of large-scale modelling results for desertification, future development on desertification control; and improvement of sustainable land use planning in half dryness and dryness regions (Zhang and Huisingh, 2018).
In the context of lacking monitoring and quantitative assessment, long-term historical changes of desertification have only been investigated in China, Myanmar, Kazakhstan, and Kuwait (Table 2). Meanwhile, future climate projections have recently been undertaken for some countries in W Asia (Cyprus and Turkey) and C and E Europe (Hungary), S Asia and C Asia. The above analyses of historical changes indicated an enhanced desertification in Myanmar, Kazakhstan and Kuwait, while climate projections have revealed that future climate in S Asia, C Asia and parts of W Asian; and C and E Europe would facilitate the development of desertification (Table 2). Countries that suffered from desertification issues are trying their efforts on controlling and mitigating the effects, with positive results occurring in China that has been witnessed to reduce the level of severity on desertification during the last few decades (Zhang and Huisingh, 2018, Feng et al., 2019). In particular, after 2000s, this reflects if the government implements the land-use conservation, land-use restriction, green space, and forest and vegetation conservation schemes.