Lakes are extraordinary ecosystems that provide societal benefits from recreation to food to clean and plentiful drinking water. But the same characteristics that draw us in leave lakes vulnerable to human activities that can damage these environments, and in some cases, cause large, abrupt, and undesirable ecological changes. The goal of the North Temperate Lakes Long-Term Ecological Research Program (NTL-LTER) is to understand how and why lakes change over time and determine the consequences of these changes. For 40 years, the NTL-LTER has studied two sets of Wisconsin lakes and their surrounding landscapes. One group of lakes is located in the rural, forested, and tourist-dominated Northern Highland Lake District in northern Wisconsin and the other is situated in the agricultural and urban landscape around Madison, Wisconsin’s state capitol. Studying these two distinct groups of lakes and being able to document changes occurring over several decades provides essential information about how different types of lakes in different settings are affected by phenomena such as shifting climate conditions, urban expansion, the arrival of invasive species, harmful algal blooms, or changes in environmental policies. These research activities, in turn, improve current understanding and management of lakes, benefitting anyone concerned with the future of the region, its freshwater resources, and the welfare of its residents. Results are also integrated into multiple K-12, undergraduate, graduate, and continuing education activities. The NTL-LTER program is committed to supporting diversity in science, and to outreach efforts that communicate scientific findings to interested individuals, non-governmental organizations, academics, and local, state, tribal and federal agencies.

New research activities will build on NTL-LTER’s strong foundation of long-term observations and deep ecological understanding of north temperate lakes to address the overarching question: What are the causes and consequences of abrupt ecological change in lakes and their surrounding landscapes? Research activities are organized around a central framework of abrupt ecological change intended to reveal mechanisms that lead to abrupt ecological changes in lakes, and involve studies inspired by four focal questions: (1) What are lake phenological responses to a warmer and more variable climate that may lead to abrupt ecological change? (2) How do interactions of land use and long-term climate change affect urban aquatic ecosystems? (3) How do external drivers interact with aquatic invasive species to regulate water quality? And (4) What causes intentional ecosystem manipulations to persist, revert, or lead to novel states? These questions consider ecological changes from organisms to ecosystems and provide potent opportunities to test, modify, and expand hypotheses regarding the causes and consequences of abrupt ecological change that are broadly relevant across diverse ecosystems.

This award reflects NSF’s statutory mission and has been deemed worthy of support through evaluation using the Foundation’s intellectual merit and broader impacts review criteria.