# The Impacts of Human Activities on Ecosystems within China's Nature Reserves
## 1 Introduction  
More than 85% of the vulnerable or endangered species are influenced by the degradation or destruction of habitat, and at least 20% are impacted by severe weather conditions and climate change in terrestrial ecosystems [1; 2]. Protected areas (PAs) are identified as the most important units for preservation in situ [3]. With increasing human activity pressure on the earth's resources, an effective PAs system is one of the most important approaches for the protection of biodiversity [4; 5; 6], or slowing the loss rate with its value from a social perspective is changing due to a constantly changing society [7]. As an increasing trend in conservation, research about PAs have become increasingly more important [8].  
The validity of PAs increasingly threatened by human activities and climate change. However, the extend of this threat is not clear. In the last few years, there have been some debates on itsvalidity [9; 10]. In the context of climate change, the advantages of PAs have been questioned for biodiversity because PAs are motionless static, whereas the distributions of plant and animal species are dynamic [11]. Climate change and land cover changes (LCC) both impress vegetation-structural properties in terrestrial ecosystems [12]. Past research has mainly concentrated on the effect of climate change [13; 14; 15]. Compared with studies which focused on the impact of climate change, the number of studies which concentrate on expected influence of future LCC on biodiversity falls far behind [2].  
In addition, the decline of biodiversity is affected by types of human drivers, including LCC, invasive species, overexploitation, and pollution [1; 16]. The most immediate and significant threats to biodiversity are direct degradation and destruction of habitats caused by LCC [2]. Threatening up to 44.8% of vertebrate populations [17], whereas climate change only is a threat to 7.1% of the extinction of vertebrates. Road construction, real estate development, and urbanization affect negatively reserves and reduce the effective extent of reserves [18; 19]. Concern that some PAs might be \"paper parks\" which hardly come sustainable protection [20; 21].  
National nature reserves (NNRs) are the most strictly managed type of PAs, which limit or even forbid human activities within their boundaries. China's environmental bulletin of 2015 suggest that China established 2740 nature reserves with area of 1.47 million km\({}^{2}\) totally which cover 14.8% of China's territory as of 2015, and China strives to take 20% of its land under protection by 2020. It is necessary to understand the dynamics of habitat in NNRs and analyze the impacts of increasing human activities on the habitat with the changing climate. However, national-scale assessments of habitat and ecosystems in NNRs is lacking. Choosing typical NNRs as research areas, this study analyzed the temporal and spatial variations of LCC, vegetation fraction (VFC) and net primary productivity (NPP) based on model simulation, remote sensing inversion and spatial analysis methods, to present the habitat ecosystem dynamics of NNRs in varied climate zones. We also used Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) nighttime light data which can detect small plot of residential land and human disturbances (HD), which means the degree of surface change to quantitive human activities in NNRs. Then HD and its relationship with VFC was comprehensively discussed to recognize the impact of human activities. The study aimed to discriminate the negative and positive impacts of human activities on habitat in China's typical NNRs over the past few decades and to assess the effects of the most strictly managed PAs in conserving habitat.