Abstract
The Mongolian Plateau (MP) plays an important role in the global carbon
cycle and has significant impacts on the ecological security of
northeastern Asia. Affected by land degradation and desertification, the
vegetation cover on the MP experiences major changes under the influence
of human activity and climate change. In contrast to previous holistic
studies on the MP, this research focusses on the features of vegetation
cover and divides the MP into three subregions (desert, grassland, and
forest) to analyze vegetation dynamics and identify the driving factors
behind vegetation change in this region. The residual analysis method is
used and its “errors” are discussed. The results show the following.
1) The area of vegetation restoration is larger than the area
experiencing vegetation degradation, and, overall, vegetation is
greening and vegetation degradation is tending to reverse on the MP. 2)
The ranking of vegetation change intensity is forest >
grassland > desert subregions. 3) Climate change is the
principal control on vegetation restoration across the whole MP,
including the grassland and forest regions. Human activity similarly
affects both vegetation restoration and degradation, but the effect of
human activity is greater than that of climate change in the desert
region. This research confirms that vegetation restoration activity is
effective in the desert subregion of the MP.
Keywords : vegetation dynamics, climatic factors, RESTREND
method, Mongolian Plateau, Driving factors
1 INTRODUCTION
Land degradation can cause global environmental change via its impact on
the terrestrial ecosystem, hydrologic cycle, energy exchange, and other
processes, and represents a major global environmental problem that
encompasses regional ecological security and food security. The
relationships that link fragile eco-environments, land degradation, and
poverty can restrict regional socio-economic development (Gao and Mao,
2003; Tong and Long, 2003). The Committee for Development Policy (CDP)
has developed a series of Sustainable Development Goals (SDGs) and SDG
15 (“Life on Land”) aims to combat desertification, restore degraded
land and soil, and strive to achieve a land-degradation-neutral world by
2030 (SDGs, 2015).
Land degradation is a complex phenomenon that is associated with a
reduction in land productivity, especially in arid and semi-arid areas
(Kassas, 1995). Although land degradation occurs across arable land,
grassland, forests, and other areas with production capability (Liu,
1995), the essence of land degradation is desertification (UNCCD, 1994).
Yang (1997) proposed that land degradation can be seen as a reduction in
the biological or economic production capacity of land caused by
excessive human activity, and that the primary problem that drives land
degradation is desertification. Zhu (1994) defined land degradation as
the decline of land productivity and the evolution of other landscapes
towards desertification, caused by unmitigated economic activity in a
fragile ecological environment. Zhou and Pu (1996) suggested that land
degradation includes desertification, which is a part of land
degradation. However, these different interpretations of what
constitutes land degradation all include the central tenet that land
degradation causes a decrease in the land productivity. Researchers have
reached a consensus that land degradation has a serious impact on global
economic and social development, which will be difficult to recover from
over a short period of time (Okin et al., 2001). In addition, without
any control measures, land degradation will accelerate, and the cost of
later rehabilitation will increase exponentially (Glantz and Orlovsky,
1983).
Land degradation is driven by a combination of human activity and
climate change. Global warming has decreased the growth of vegetation in
some regions (Wieder et al., 2015), and reduced vegetation productivity
to some extent (Asseng et al., 2015). Temperature, precipitation, wind
speed, and other climatic factors influence regional soil, vegetation,
and other surface characteristics, leading to climate-related vegetation
degradation (Guo et al., 2012). Compared with climatic factors, it is
difficult to quantify the direct impact of human activity on vegetation
change. Rapid population growth, industry development, animal husbandry,
and ecological restoration projects all have some impact on vegetation
change. All anthropogenic activity, such as deforestation, mineral
exploitation, and improper land use, as well as emissions of industrial
and domestic waste, and greenhouse gas emission, break the balance of
natural ecosystems and result in serious ecological and environmental
problems (Fleskens and Stringer, 2014; Liu Q. et al., 2014).
The Mongolian Plateau (MP) is located in the hinterland of Eurasia,
which spans arid, semi-arid, and semi humid climate regions. This unique
geographical location makes the eco-environment of this region
especially vulnerable to interference from external factors. The MP is
often used to study land degradation because the region is sensitive to
both human activity and climate change, and also faces the problems of
desertification and vegetation degradation (Zhang et al., 2008). The MP
plays an important role in the global carbon cycle, and its ecosystem
status and changes have an important impact on the environment of the
whole of northeastern Asia (Zhang, et al., 2009; Zhang, et al., 2003).
Changes to the eco-environment of the MP will affect carbon sinks in the
surrounding regions, as well as further afield, through dust
transmission. In recent decades, in the context of global warming and
excessive reclamation, overgrazing, poor protection, soil degradation,
and desertification of the MP have increased, resulting in severe
pressure on the ecological environment (Liu, et al., 2016).
Consequently, financial resources and policy measures have been
implemented in an attempt to protect and improve the ecological
environment of the MP, and these countermeasures have been relatively
effective. However, soil degradation and desertification in the region
remain very serious problems, and directly threaten the ecological
security of China and the whole of East Asia (Mi et al., 2015; Fujiwara
et al., 2007). Using the MP as our research focus to study vegetation
change has important and urgent practical significance for regional
vegetation restoration and ecological security in Southeast Asia.
There are regional differences in the extent and impact of the various
factors that influence vegetation change. Smaller scale causes of
vegetation degradation on the MP have been somewhat overlooked due to
the focus on larger regional effects in previous research. Therefore, it
is necessary to develop a clearer picture of the factors that drive
vegetation dynamics in the different types of ecosystems on the plateau.
In this study, we aim to determine the nature of vegetation change and
identify its key drivers across the whole plateau and in each of its
subregions (i.e., the desert, grassland, and forest subregions).
2 MATERIALS AND METHODS