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Alternative stable states in large shallow lakes?
Janssen, A.B.G. ; Teurlincx, S. ; An, S.Q. ; Janse, J.H. ; Paerl, H. ; Mooij, W.M. - \ 2014
Journal of Great Lakes Research 40 (2014)4. - ISSN 0380-1330 - p. 813 - 826.
catastrophic regime shifts - ecosystem model pclake - drinking-water source - detroit river system - taihu lake - fresh-water - aquatic vegetation - spatiotemporal patterns - macrophyte communities - spatial heterogeneity
Many lakes worldwide are experiencing great change due to eutrophication. Consequently, species composition changes, toxic algal blooms proliferate, and drinking water supplies dwindle. The transition to the deteriorated state can be catastrophic with an abrupt change from macrophyte to phytoplankton domination. This has been shown repeatedly in small lakes. Whether such alternative stable states also exist in large shallow lakes is less clear, however. Here we discuss the characteristics that give rise to alternative stable states in large shallow lakes either in the lake as whole or restricted to specific regions of the lake. We include the effect of lake size, spatial heterogeneity and internal connectivity on a lake's response along the eutrophication axis. As a case study, we outline the eutrophication history of Lake Taihu (China) and illustrate how lake size, spatial heterogeneity and internal connectivity can explain the observed spatial presence of different states. We discuss whether these states can be alternatively stable by comparing the data with model output (PCLake). These findings are generalised for other large, shallow lakes. We conclude that locations with prevailing size effects generally lack macrophytes; and, therefore, alternative stable states are unlikely to occur there. However, most large shallow lakes have macrophytes whose presence remains unexplained when only size effect is taken into account. By including spatial heterogeneity in the analysis, the presence of macrophytes and alternative stable states in large shallow lakes is better understood. Finally, internal connectivity is important because a high internal connectivity reduces the stability of alternative states.
Methods and tools for integrated assessment of land use policies on sustainable development in developing countries
Reidsma, P. ; König, H. ; Feng, S. ; Bezlepkina, I. ; Nesheim, I. ; Bonin, M. ; Sghaier, M. ; Purushothaman, S. ; Sieber, S. ; Ittersum, M.K. van; Brouwer, F.M. - \ 2011
Land Use Policy 28 (2011)3. - ISSN 0264-8377 - p. 604 - 617.
nutrient management - zhejiang province - cropping systems - european-union - farm models - lake region - taihu lake - rice - china - asia
For stimulating sustainable development in developing countries, land use patterns and land use changes are considered critical, and therefore effective and efficient land use policies are needed. In this paper we present a methodological framework that has been developed in a joint European and developing countries project (LUPIS – Land Use Policies and Sustainable Development in Developing Countries), to assess the impact of land use policies on sustainable development in developing countries. An illustrative application is presented for a case study in China, where water pollution due to agriculture in Taihu Basin is a major problem. We argue that an integrated assessment is required, considering multiple drivers and indicators that determine the objectives and constraints of the stakeholders involved. Therefore, the sustainability impact assessment (SIA) is based on the concept of Land Use Functions (LUFs), and impacts on these LUFs are discussed with stakeholders based on a multi-criteria analysis. LUFs comprise economic, environmental and social indicators relevant for stakeholders at multiple scales. Instead of focusing only on the indicators that determine the problem (e.g., nutrient leaching in the Chinese case study), we take a broader perspective (considering also social, economic and institutional objectives and constraints), such that feasible policy options can be recommended. Stakeholders have a large role in discussing the selection of indicators and policies (pre-modelling), evaluating the impacts on indicators (modelling), and the weighing of indicators and LUFs (post-modelling). For the assessment of impacts on indicators (modelling), quantitative and qualitative approaches are combined. We present and discuss an impact assessment of policy options in Taihu Basin, for the current situation and towards 2015. The methodological framework as presented here proved to be useful to guide a sustainability impact assessment in China and six other case study regions.
Spatial and seasonal variations of the contamination within water body of the Grand Canal, China
Wang, X.L. ; Han, Jingyi ; Xu, L.G. ; Zhang, Q. - \ 2010
Environmental Pollution 158 (2010)5. - ISSN 0269-7491 - p. 1513 - 1520.
land-use - taihu lake - long-term - chemistry - sediments - pollution - quality - metals - river - hangzhou
To delineate the character of contaminations in the Grand Canal, China, a three-year study (2004-2006) was conducted to investigate variations the water quality in the canal. Results showed that the variation of water quality within the Grand Canal was of there is remarkable spatial and seasonal heterogeneity regarding water quality within the Canal. Values of contaminants in dry-season were obviously higher than those in wet-season. Sites influenced strongly by industry and urbanization showed higher contents of nutrients and lower levels of dissolved oxygen in water body; moreover these sites were severely polluted by dissolved metals with the contents of cadmium, chromium and copper exceeding the Criteria Maximum Concentration (CMC), US EPA. Multivariate statistical analysis suggested nutrient and dissolved metals pollution was the dominant environmental problems within the Canal. Anthropogenic influences played a dominant role in the character of contaminations in the Grand Canal.