Evolution Characteristics of Wetland in Beijing and Its Driving Factors Analysis

摘要

Supported by remote sensing and GIS technology, using Multi-temporal TM images from 1984a to 2008a in Beijing, the dynamic evolution characteristics of wetland were analyzed and driving factors were explored. The result shows: the total wetland area increased during the period from 1984a to 1996a, the wetland area in 1996a had the maximum value, totally 605. 67km~2. while it obviously declined at the annual average rate 6.7% from 1996a to 2004a, the wetland area in 2004a was just 285.27 km~2, which accounting for 47.1% of the wetland area in 1996a. Wetland had taken the dominant shrinking trend and its ecological function had degenerated gradually. The total wetland area had appreciably increased after 2006a. reaching to 318.39km~2 in 2008a. It was classified to natural wetland and artificial wetland, natural wetland means river wetland and artificial wetland included reservoir wetland, pond and paddy field wetland, artificial canal wetland and city lake wetland. The proportion of artificial wetland area was lager than natural wetland, which played the ascendant function, accounting for about 70.95 to 86.01 percents in area. Wetland area increased from 1984a to 1996a mainly because of adequate precipitation; while the total wetland area declined from 1996a to 2004a for both natural elements and artificial reasons. Natural reasons included continuous dry climate, higher transpiration and decrease of water inflow from upriver. With the urbanization process acceleration, the population increased 1.52 times between 1984a and 2008a, which further lead to the wetland area loss and water resource consumptions. The total area of wetland in 2006a and 2008a increased appreciably as a result of the implement of positive policy and precipitation's increase.