China is characterized by a continental monsoon climate, and most parts of China have a wider range of seasonal temperature change compared with other continental areas at the same latitude. Many places in China are cold in winter and hot in summer, and high temperatures generally prevail in the country at large in summer. Precipitation is unevenly distributed in time and space, concentrating in the flood season, and annual precipitation decreases from the southeast coast to the northwest interior. China has a fragile eco-environment, with serious soil erosion and desertification and a forest coverage rate of 18.21 percent, only 62 percent of the world's average. The area of natural wetlands is comparatively small; most grasslands are highly frigid meadows and desert steppes; temperate grasslands in northern China are in danger of de-generation and desertification due to the impacts of drought and deterioration of the eco-environment. With a coastline over 18,000 km long, China is vulnerable to the adverse effects of sea level rises.