Extending the timescale and range of ecosystem services through paleoenvironmental analyses: the example of the lower Yangtze basin
In China, and elsewhere, long-term economic development and poverty alleviation need to be balanced against the likelihood of ecological failure. Here, we showed how paleoenvironmental records can provide important multidecadal perspectives on ecosystem services (ES). More than 50 different paleoenvironmental proxy records can be mapped to a wide range of ecosystem services categories and subcategories. Lake sediments are particularly suitable for reconstructing records of regulating services, such as soil stability, sediment regulation, and water purification, which are often less well monitored. We demonstrated the approach using proxy records from two sets of lake sediment sequences in the lower Yangtze basin covering the period 1800–2006, combined with recent socioeconomic and climate records. We aggregated the proxy records into a regional regulating services index to show that rapid economic growth and population increases since the 1950s are strongly coupled to environmental degradation. Agricultural intensification from the 1980s onward has been the main driver for reducing rural poverty but has led to an accelerated loss of regulating services. In the case of water purification, there is strong evidence that a threshold has been transgressed within the last two decades. The steep trajectory of the regulating services index implied that regional land management practices across a large agricultural tract of eastern China were critically unsustainable.
Over the past decade, ecosystem services have become central to discussions about the sustainable management of natural resources. A key review of the science for managing ecosystem services highlighted the need for “networked, place-based and long-term social-ecological research” (p.1309). However, critical data needs include comprehensive time series information for major social and ecological states covering a range of appropriate timescales. Such views were already held by the Millennium Ecosystem Assessment, for example “the weakness in documentation and information on regional trends remains a serious handicap” (p. 837), and have recently been reiterated in the Council of Scientific Union reports dealing with Earth System Science for Global Sustainability. The UK National Ecological Assessment also highlighted the gaps in information about trends that exist despite a science infrastructure that has supported the regular monitoring of many aspects of the UK environment.
Alternative sources of data for ecological change over the last few decades and centuries lie in natural archives, such as lake sediments. The paleoenvironmental community, comprising paleoecologists, paleolimnologists, and geomorphologists, has generated large amounts of proxy data that reconstruct different ecological and functional processes and services in many regions of the world. Over the past 50 years the ability to interpret sediment records as proxies for specific environmental processes has become increasingly refined, with the use of multivariate statistics and modern-day calibrations. Paleoenvironmental research has long been concerned with climate and human impacts on natural processes but has yet to fully embrace the ecosystem service agenda that demands integration of social and ecological records. Despite several papers referring to how paleoenvironmental records may be used with respect to specific ecological issues, like biodiversity and conservation, there is no review of the scope and application of multiproxy records to the study of ecosystem services. In national/international reports dealing with ecosystem services, paleoenvironmental proxies are usually confined to reconstructing past climate. The aim of this paper was to rectify this situation with a case study using paleoenvironmental and socioeconomic records from the lower Yangtze basin, China.