Land Type Changing———A Saboteur of Ecosystem

张伟豪 冯瑞林 康丹 郑天铭 蒋磊

Abstrct：Nowadays，engineering construction tends to pay more attention to economic benefits，and neglect environmental degradation costs. The third largest freshwater lake （Taihu Lake）in China was selected as the research object，and three typical land change processes occurred in the Taihu Lake basin in recent years. Enlargement of farmland in 1997，Construction of Huzhou industrial park in 2007（big scale project）and Construction of Taihu resort in 2013 （small scale project）.

Model 1：an environmental degradation assessment method based on the value of ecological services，quantifies the impact of projects of different specifications on the environmental value，and calculates the cost of environmental degradation. In model 1，6 factors were selected，namely，water supply value，aquatic product supply value，water purification value，water environment regulation value of plankton，soil regulation value of terrestrial organisms and habitat value. The 6 ecological values were calculated with different evaluation methods. It is found that the environmental degradation cost of the construction of the industrial park in the three typical land changes is the largest （1579.29 million yuan），while the construction cost of the small-scale Taihu resort is the smallest （25414.01 million yuan）.

Introduction

It is easy to ignore the negative effects of development while developing the economy. Whenever people start engineering and change the ecosystem，ecosystem services have to be removed.It is called environmental degradation. In considering the costs of environmental degradation we need to quantify the factors that affect ecological services. These assessments of environmental degradation are rarely included in engineering considerations. Therefore，while striving for economic benefits and people's livelihood convenience，developers should pay more attention to the impactof construction projects on surrounding environment. Therefore，when our ICM team participated in the project design，it was necessary to establish an ecological service evaluation model，which considered the environmental degradation cost in addition to the project operation cost，so as to understand the real economic cost of land use while providing ecological services.

Sensitivity Analysis -- Evaluate the Effectiveness of model

The atmospheric regulation formula of plankton in model 1 is as follows：

V A Pf（Pc 2.666 P0）

Run the model once every time the parameter value is changed，and output Pc measure the variation of the corresponding amount of aquatic plants was used as the basis for the sensitivity analysis. Other sensitivity calculation procedures and Pc measure he sensitivity coefficients of each factor can be calculated according to the similar sensitivity calculation process.

As can be seen from the table：phytoplankton regulate atmospheric changes and P 0The change in theta is inversely proportional to P0 The amount and value of hydrophytoplankton decrease with the increase of. The change of quantity and value of hydrophytoplankton is positively proportional to the change of other parameters. Among the parameters analyzed，the carbon sequestration cost has the largest impact on the model，while the lake area has the smallest impact. According to the analysis results，the order of the sensitivity of the parameters is：carbon sequestration cost > carbon cost coefficient > oxygen release cost > lake area

Model 1

research objects，ideas and methods

When considering the impact of projects of different scales on the environment，it is necessary to evaluate the different values of the Taihu lake ecosystem. The team summarizes six factors that have a direct impact on the ecosystem service value，and selects different evaluation methods to evaluate the cost of environmental degradation.

supply service value

The supply and service of Taihu ecosystem means that Taihu lake can provide water source and aquatic products for human beings，which can generate service value at the same time. Supply value is divided into two categories：water supply value，aquatic supply value.

plant regulatory value

The atmospheric regulation of the Taihu lake ecosystem is mainly divided into two categories：one is the fixation of co2 and the release of oxygen generated by the photosynthesis of aquatic plants in the lake body；the other is the regulation of terrestrial plants around the lake body on the soil

① Aquatic plants regulate the atmosphere

To study the economic benefits of co2 fixation and oxygen release generated by photosynthesis of plants in the lake，the cost of carbon fixation，the cost of oxygen release，the size of the lake body，the amount of co2 fixation and other factors should be considered. It is known that plants can release 2.666g of oxygen for every 1g of carbon fixation during photosynthesis.

CO2 （264 g）+ H2O（108 g） C6H12O6 （108 g）+ Oz

The value estimation model of aquatic plants can be listed

V A Pf （Pc2.666P0）

Chlorophyll A in plankton in the lake body is lower than the critical value chl0. The empirical formula is usually used to calculate the productivity of lake body plants

Pf 34.52chl 222.9

The lake area is 2338km2Therefore，the value estimation model of aquatic plants can be simplified as follows：

V 1.6 1010 8 chl 109

Can calculate the atmospheric regulatory value created by 18 years of aquatic phytoplankton：

Soil nutrient value

The main nutrients in soil are nitrogen，phosphorus and potassium，and the loss of these three elements is considered when soil quality declines. A model was constructed based on nutrient loss in soil

M a Ss P M h

Which Ma is the total value of nutrient loss in soil，P refers to the content of N，K and P in the soil layer of unit area，and the measured content of N，K and P in the 0-60mm soil layer is 950.12kg/hm2，Mh refers the average market value of fertilizers is 2550 yuan/t，from which the total value of nutrient loss in soil can be calculated as shown in the table below.

Conclusion

Three typical changes of land use types around Taihu lake were studied. The cost of environmental degradation was quantified through the construction of two models. The model 1 based on the value of ecological services concluded that the cost of environmental degradation in 1997/2007-2013 was 16016.97 million yuan，25414million yuan and 1579.29 million yuan，respectively. According to PSR model 2 based on environmental performance assessment，the environmental degradation costs of three projects of different scales are respectively 25625.34 million yuan，40658.56million yuan and 25267.89 million yuan. It can be seen that the solution range of model 2 is larger than that of model 1.

Through the sensitivity analysis of the environmental degradation cost caused by the water purification value in the model，it is found that the sensitivity is followed by carbon sequestration cost，carbon cost coefficient，oxygen release cost and lake area from the largest to the smallest，that is，carbon sequestration cost has the most significant impact on the water purification value.

The use of the model in this paper needs to take into account the change of model parameters caused by the decrease of pollutant treatment cost brought by scientific and technological progress，or the need to adjust the model when new pollutants appear.