To humidify the dry air
　　In dry season， our skin and nasal cavity will fell discomfort， if we put a basin of water in the room， the discomfort will be alleviated. And wetlands， especially those surrounding the city， are like natural humidifiers， which can greatly increase the air humidity.
　　The function of wetlands to increase air humidity mainly dues to its open water surface and the surrounding mud coast and vegetation. The open water surface can increase evaporation， then what are the roles of the mud coast and vegetation？ On one hand， the mud coast has lower sunshine reflectivity， therefore， it has better warming effect than water； on the other hand， in the mud coast， the gaps between soil particles are formed， the uneven surface also greatly increases the evaporation area， resulting in higher evaporation capacity. Meanwhile， the mud coast is also a good area for a lot of wetland plants to grow， the plants also greatly increase the evaporation capacity through their powerful transpiration. Take the most common wetland plant reed as an example， about 800 kg water will be rising if 1 kg of reeds grow up， such a high transpiration will greatly improve the surrounding humidity of the wetland.
　　To cool down
　　the city with fever
　　As we all know， water has a huge heat capacity， that is to say， absorbing the same heat， the temperature of water rises smaller； at the same time， water has a high heat of evaporation， which means when water vapors， it will absorb a lot of heat. Therefore， with the increase of air humidity， the wetlands can effectively reduce the surrounding environment temperature.
　　In the city， because of the frequent human production activities， and the constructions and roads changing the original characteristics of the environment， making the temperature is usually higher than the suburbs， forming the so-called "heat island effect". The heat island effect increases the discomfort of people living in the city to some extent， so the wetlands， especially the urban wetlands are very important. The existence of the wetland can significantly reduce the temperature of the surrounding environment， creating a cool place in the heat island. For example， the temperatures around Kunming lake in summer of Beijing is 5 ～ 6Co lower than those of the urban center， and even such small wetland as Taoran pavilion lake will reduce the temperature by 2 ～ 3 Co. These areas will become the leisure summer resort for people. 　　"Swallow" the carbon dioxide
　　Although forests and oceans are the main forces to absorb carbon dioxide， the function of wetland cannot be ignored. Why can wetlands absorb and store carbon dioxide？ That is because the wetland provides a good growth environment for a large number of plants， the growth of plants needs carbon dioxide， and convert them into carbon in plants. When the plants die， the dissimilation of plants in the wetland is slower， which slows down the releasing of carbon dioxide， therefore， the wetlands become the carbon storage. According to the measure， the wetland in Beijing city will fix 15000 tons of carbon a year. These fixed carbon and the emissions of oxygen will improve the surrounding environment of air quality， also bring a significant ecological value. This means the wetland vegetation absorb carbon dioxide and increase the capacity of carbon dioxide to the atmosphere， thereby increasing the emissions of carbon dioxide into the atmosphere in the process of production. In accordance with the international carbon emissions quota， fixing the carbon means creating the economic value of about 325 million yuan. Seen from this perspective， the wetland is of considerable ecological value.