Research progress and prospects of karst ecosystem services

Karst ecosystems are typical vulnerable ecosystems in the world. The variety of ecosystems provides multiple important services such as water conservation, soil retention, biodiversity, grain production, water supply and leisure entertainment for humankind. However, excessive and unreasonable human activities in recent years has seriously destroyed karst ecosystem structure and influenced the effectiveness of karst ecosystem services. In order to clarify current situation and existing problem of karst ecosystem service research, this paper provides an in-depth overview in the progress and prospect of karst ecosystem service research on the basis of throughout literature and reference material surveys. The results showed that current classification of karst ecosystem service research has mainly transplanted the results of other fields, which ignored the particularity of karst ecosystems. The objects of assessment are water and soil conservation carbon fixation and forest products, but rarely involve cultural services. Quantity of value and material methods were widely applied in assessment of karst ecosystem services, whereas there was a lack of ecosystem service assessment based on these ecosystem processes. Current researches have much paid attention to spatial heterogeneity of karst ecosystem service value on the meso-small scale, while ignored the large-scale research. Research paradigm of karst ecosystem services was that the effects of land use change in ecosystem services value, which underlined the effects of land use changes and ecological projects on karst ecosystem services value. Few scholars paid close attention to the effects of climate change as well as coupling effects of natural factors and human factors on karst ecosystem services. We should enhance the study of karst ecosystem services based on the framework of "ecosystem structure and process-ecosystem function-ecosystem service" and establish unique classification system of karst ecosystem services. The applicability of the evaluation method of ecosystem services and development and utilization of evaluation model in karst region should be emphasized. Ecosystem services assessment in karst region at a large scale and associated cultural services assessment should be strengthened. We should expand the study of balance and synergy among karst ecosystem services as well as the effects of karst ecosystem services on human welfare. Spatial and temporal heterogeneity of tradeoff and synergy as well as the application of new techniques in tradeoff and synergy research should be given with more attention. Future research should attach great importance to comprehensive index system of human welfare and relationship between karst ecosystem services and human welfare in karst region. Finally, quantitative analysis of the impacts of natural factors and human factors on karst ecosystem services should be enhanced. 