This thesis focused on biodiversity loss in arable farming systems of North-East Taihu Lake Basin, China. Rice farming has been conducted around the basin for nine centuries due to availability of fertile soils and wet conditions. These contributed to economic development and have been sustaining one of the most densely populated areas in China. The Basin has witnessed significant ecological changes in the history of rice cultivation since the 1940s, as a result of population growth, the adoption of industrial technologies such as chemical fertilizers and pesticides, and changes in rural policy and its implementation. These different types of changes at different spatial and temporal scales have been widely resulting in pressures on biodiversity in rice agricultural landscapes of TaihuLakeBasin.
The objective of this study was to assess the impacts of agricultural intensification on biodiversity in paddy agro-ecosystems in the Basin, achieved by (a) developing a methodological framework, (b) literature review, (c) combining results from a variety of studies, and (d) statistical analysis of farm survey data. Together these led to an assessment of biodiversity loss in the Basin in the current situation. The framework of Firbank et al. (2008), distinguishing three processes influencing biodiversity, was adopted. These pressures are: land use change at regional scale, landscape structure at landscape scale, and crop management at farm scale.
At regional scale, conversion of paddy field into urban area with constructions was the main threat for biodiversity, and its driving factors were mainly economic development in rural areas and urbanization. Rapid conversion threatens biodiversity and thus the assessment of land use change on biodiversity is essential. To assess biodiversity loss, the application of ecosystem quality (EQ) by Reidsma et al. (2006) and biodiversity intactness index (BII) by Sholes and Biggs (2005) is potentially effective, but precise evaluation requires more detailed information on land use and functionality, mainly obtained from the observations at landscape and farm level.
The availability of semi-natural elements is considered as one of the most important contributors to biodiversity protection in the context of landscape structure. My assessment of semi-natural elements at one village landscape in North-WestTaihuLakeBasin, however, revealed that availability of semi-natural elements was low, implying low biodiversity richness.
At farm level, variability in fertilizer use was investigated as the indicator of agricultural intensity which impacts negatively on biodiversity. In Wuxi, Changzhou, and Zhenjiang municipalities, farmers start adopting a new fertilization strategy, called, formula fertilizer. The proportion of N, P, and K in formula fertilizer is adjusted to soil fertility level of each farmer’s field, and thus it is expected to result in decreasing amount of fertilizer application due to more efficient use of fertilizers. Statistical analysis of collected farm survey data on fertilizer use, however, showed no reduction in fertilizer application and still excessive use in the whole region. The result indicates that intensity of crop management was relatively high, indicating continuous high risk for biodiversity loss.
Results from literature reviews and statistical analysis of empirical data show that the agricultural systems in North-WestTaihuLakeBasin are very intensive at all three dimensions and therefore biodiversity is likely to be low. With the objective of conservation at regional scale, efforts need to be put through two strategies: increasing natural area, and controlling paddy fields loss. Further research is required to assess the newly implemented policy of converting lands around the watersides into areas with trees. Other efforts also need to be focused on the interaction between farm management and landscape structure since less intensive management and improving quality and quantity of semi-natural areas are the key aspects of conserving biodiversity around paddy fields. The practical implementation of formula fertilizer is still far from efficient nutrition management. Thus policy should focus on the promotion of improved formula fertilizer, e.g. though extension services.