I grew up between the Great Lakes and the Finger Lakes, and for the first two decades of my life my perception of lakes was probably similar to that of most other people: lakes were lovely to look at, an ideal spot to build a house, restaurant, or vineyard, perhaps a place to go boating or swimming on a sweltering summer afternoon. But the muck at the bottom? I never thought twice about it. It turns out that mud can tell stories. Hidden in that sticky matrix of clay, silt, sand, and organic goo are clues to the past. Those clues provide valuable information to scientists like myself. Paleolimnology is a multi-disciplinary field that endeavours to reconstruct the history of lakes and other inland water bodies, often in relation to regional paleoclimate or (pre-) historic events. To do so, researchers can analyse a range of geological, chemical, and biological characteristics of sediment cores that help tease out ancient tales of environmental change. My own work has focused on environmental and hydrologic changes in Cambodia, including the ancient city of Angkor, over the last two millennia. Lake sediments haven’t often yielded headline-grabbing findings (though political satirist and comedian Stephen Colbert did place the Journal of Paleolimnology “on notice” in 2006). But, paleolimnology’s obscurity is fading. Lake mud can do more than tell stories about the past; it can be a potent tool for protecting our future, as well. In 2000, a piece of environmental legislation called the EU Water Framework Directive (WFD) was enacted. Essentially, this law tasks EU counties with restoring all their water bodies to “good status” by 2015. But, how do we know what a “good status” might be for a particular body of water? That’s where paleolimnology comes in. Lake sediment records can provide an indication of a baseline, or reference condition, which can be used to achieve restoration targets such as those set out by the EU WFD. Much of this research was carried out within Euro-limpacs, a project set up to help understand how climate change affects aquatic ecosystems. The results generated by Euro-limpacs (which ended in 2009) and its successor REFRESH are useful for implementing not only EU legislation like the WFD, but other multilateral environmental agreements as well, such as the Ramsar Convention and the UN Convention of Biological Diversity. Paleolimnology also plays a role in assessing ecosystem services. Ecosystem services are the benefits human derive from the environment, which includes resources like food and water, processes such as nutrient cycling, as well as other assets like aesthetic value. Earlier this month, TEEB (The Economics of Ecosystems and Biodiversity) released a report that examined ecosystem services related to water and wetlands. The report reiterates water’s critical importance to human well-being, but also stresses that water-related ecosystem services need to be incorporated into water management strategies around the world. How can mud help address this? Lake sediment records can preserve signals related to a number of ecosystem services, such as water quality, air quality, plant diversity, or soil stability. Recently, a group of researchers from the Ecosystem Services and Poverty Alleviation (ESPA) programme developed a regional index of ecosystem services from lake records from the Lower Yangtze Basin in China. This index, the first of its kind, tracks the status of certain ecosystems services in the area for the last 200 years. Official records and long-term data collection related to ecosystem services don’t always exist, especially in less-developed countries. Thus, tools like this index, which can provide an alternate source of information about ecosystem services, are incredibly useful to policy and decision makers and are a valuable addition to water management strategies. The application of paleolimnology to environmental protection and water resource management is still very much in its early days. Even so, mud has already shown its potential to help address some of the more pressing challenges we face today. Never underestimate what you might accomplish by messing about in the (lake) muck. *Mary Beth Day  is doing a PhD in Earth Sciences. Picture credit: www.freedigitalphotos.net and J. Frasse.