North Temperate Lakes

Invasive species are often a major threat to native species and biodiversity, and consequently to the social value of ecosystems. In the absence of good modeling of the economics and ecology of human-caused species dispersal, identifying management policies that best serve social objectives with respect to the control and prevention of the spread of invasive species is unlikely if not impossible. This project develops an integrated economic and ecological model to examine the spread of aquatic invasive species (AIS) in a freshwater lake system where recreational boaters are the principle vector of dispersal. The model is applied to an investigation of a large lake system in northern Wisconsin.

The cycling of water between the atmosphere, ecosystems, and humans is a growing concern in urbanizing agricultural watersheds where changing climate, human demands, agricultural practices, land use and other policies interact. How will the benefits we receive from our diverse landscapes be sustained as climate, land use, cities, and human demands change? We will address this question using integrated scenarios, model experiments to assess effects of changing drivers on human benefits derived from ecosystems, evaluations of governance, public engagement, and information management. Our focus is the Yahara Watershed of Wisconsin, which is an exemplar of water-related issues in the Upper Midwest. We will address three specific questions.

The Global Lake Ecological Observatory Network is a grassroots network of limnologists, ecologists, information technology experts, and engineers who have a common goal of building a scalable, persistent network of lake ecology observatories. Data from these observatories will allow us to better understand key processes such as the effects of climate and landuse change on lake function, the role of episodic events such as typhoons in resetting lake dynamics, and carbon cycling within lakes.

This Integrative Graduate Education and Research Training (IGERT) initiative supports the establishment of a broadly-based graduate training program that will equip students to combine the social, economic and biological sciences in the study of environmental problems presented by freshwater ecosystems.  Problem areas emphasized include studies of the economic value of environmental resources, the role of humans in the vulnerability of ecosystems to natural change, the impact of irreversible environmental changes, and the effect of ecosystem features on societal interactions.  The project is a joint effort of 20 faculty from the Departments of Agriculture and Applied Economics, Civil and Environmental Engineering, Forest Ecology and Management, Limnology, Rural Sociology, Soil Science and Zoology.  Educational opportunities center on three required IGERT seminar courses, one on selected topics related to current IGERT faculty research, one on relevant research methods, and one on team research during which student teams will test hypotheses generated from the topics and methods seminars.  In addition to its education and research initiatives, the program undertook a continuous self-evaluation effort led by a faculty member from the School of Education.  IGERT provides an opportunity for the development of new, well-focused multidisciplinary programs that bridge traditional organizational barriers, uniting faculty from several departments or institutions to establish a highly-interactive collaborative environment for both training and research.

North American lakes with heavy infestations of nuisance macrophytes (e.g.- Eurasian watermilfoil, Myriophyllum spicatum) are often associated with slow growing populations of bluegill (Lepomis macrochirus) and largemouth bass (Micropterus salmoides).  Reducing macrophyte densities has often been suggested as one way of improving fish growth in such lakes.  We conducted a series of planning and modeling exercises to optimize the design of a multi-lake study designed to test the effects of macrophyte harvesting on growth of bluegill and largemouth bass.  From a large group of candidate lakes, we selected thirteen lakes in southern and central Wisconsin for study.  These had slow growing bluegill populations and were dominated by watermilfoil and other fine-leafed macrophytes.  In 1994, macrophytes were mechanically removed from approximately 20% of the littoral zone in four lakes selected for experimental manipulation.  The other nine lakes served as unmanipulated controls.  Macrophytes were removed in a series of deep channels spaced evenly around the lake with a macrophyte harvester retrofitted with a deep cutting bar to remove macrophytes at the plant-sediment interface at depths deeper than those reached with a commercial harvester.

The importance of the position of a lake in the landscape relative to hydrologic flow has been a focus of the Long-Term Ecological Research Project, based at the UW-Madison Center for Limnology, for almost two decades. We have found that there are strong patterns in water chemistry, primary productivity, and morphology driven by ground and surface water inputs (Magnuson et. al. 1990, Kratz et al. 1997, Riera et al. in press). Also, lake size and physico-chemical conditions within a lake have been shown to influence community structure in fishes (Tonn and Magnuson 1982, Tonn et al.1990). However, we know much less about how landscape level traits, such as surface water connections, influence biotic diversity and community structure within lakes and whether the species pool changes across watersheds of North-Central Wisconsin (Hrabik and Magnuson 1999). The primary goal of our project is to conduct field experiments that contrast lake chemical and geographical properties and explore the role of those properties in shaping biotic diversity and community structure.

The Northern Highlands Lake District of Wisconsin is in transition from a sparsely settled region to a more densely populated one. Expected changes offer benefits to northern Wisconsin residents but also threaten to degrade the ecological services they rely on. Because the future of this region is uncertain, it is difficult to make decisions that will avoid potential risks and take advantage of potential opportunities. The NHLD project adopts a scenario planning approach to cope with this problem of prediction. NHLD uses an ecological assessment framework developed by the Millennium Ecosystem Assessment to determine key social and ecological driving forces in the Northern Highlands Lake District. From these, they describe three alternative scenarios to the year 2025 in which the projected use of ecological services is substantially different. The work reported in the paper demonstrates how scenarios can be developed for a region and provides a starting point for a participatory discussion of alternative futures for northern Wisconsin. Although the future is unknowable, they hope that the assessment process begun in this paper will help the people of the Northern Highlands Lake District choose the future path of their region.

We live in a rapidly changing environment, yet scientists’ understanding of the ecological consequences of wholesale changes in climate and land use is in its infancy. So too is the incorporation of this knowledge into environmental management and policy, which is so critical because both climate and land use strongly affect ecosystems and the services that they provide to society.  The main goal of this research is to develop tools to measure and understand how climate and land use by themselves and as interacting factors affect lake ecosystems  across scales of time and space (cross-scale interactions), even as these factors are themselves, changing. A cross-scale interaction occurs when a factor at one scale, such as agricultural land use around a lake, interacts with a factor at another scale, such as the climate of the region the lake is located within. Such interactions can lead to situations where lakes in different climatic zones respond differently to agricultural land use in their watersheds, all else being equal.