For almost 10,000 years little changed in the nature of Wisconsin Lakes. Then, in a 150 year blink-of-a-geologic-eye, a dramatic transformation occurred. During the mid-nineteenth century, European settlers began arriving in the Upper Midwest. Native American inhabitants had been hunter-gatherers with sparse and casual crop cultivation, but the European colonists practiced row farming at a much more intensive level. Clues to the types and extent of these past land use practices can be found if we know what to look for in the sediments of our lakes.

During the 1800s, farming was tough. It meant cutting down forests and planting around stumps until they could be pulled. Work days were from dawn until dusk, and machinery was crude. As a result of these rugged conditions, a workable farm field could take years to clear. Starvation was often "waiting in the wings," and people were happy if they could produce enough products to last a Wisconsin winter. Even though it was small in scale compared to today’s standards, the intensification of farming was huge when contrasted by the Native Americans’ impact on the land. The opening of the forest allowed large amounts of sediments and nutrients to be exported from the land to the water.

Major events in the history of our country, like World War II, had definite impacts on our lakes. World War II marked another period in which agricultural practices intensified. To support the war, some factories converted their production efforts to the manufacturing of ammunition. It was soon discovered that the same chemicals used to make explosives could be used to make synthetic fertilizers. After the war, factories easily made the switch from turning out ammunition to producing synthetic fertilizers. These new fertilizers were cheap and readily available, and they became widely used in farming operations. The intensification of farming practices and use of fertilizers resulted in a higher potential for soil erosion. Nearly all lakes with significant agriculture in their watershed experienced profound changes, as sedimentation rates greatly increased and phosphorus levels rose. Ultimately, these revolutions in agriculture resulted in decreased water clarity and larger and more frequent algal blooms.

Lakes experienced a resurgence of nutrients during the 1970-90s, because of an increased emphasis on "banking" phosphorus in the soils. The government recommended that more phosphorus be added to farm fields than plants truly needed. The idea was that this reservoir of phosphorus would provide a buffer for agricultural productivity. However, in reality, much of this phosphorus washed off the land and eventually ended up in lakes. The result? You guessed it…large declines in water clarity and greater algal blooms.

In addition to agriculture, there was another source of nutrients that would come to impact our lakes…development. Our love for lakes has fed a slow, but steady, increase in cottage and home construction, starting in the early part of the twentieth century. In southeastern Wisconsin, improvements in highways and automobiles allowed people to live farther from their work places. With cheap, easy transportation came the construction of larger permanent homes around area lakes. While cottages constructed during the early part of the twentieth century delivered relatively small amounts of sediment and nutrients, the "reconstruction" in the second half of the twentieth century resulted in considerable increases in the amounts of sediments and nutrients coming into the lakes. Although this increased development was detrimental to the lake’s water quality, it produced less runoff than agricultural activities. Therefore, lakes where the nearby land use was converted from agricultural to residential often experienced improved water clarity.

In the northern part of the state, cottage development was nearly absent until the late 1920s. Prior to this time, widespread logging was the cause of major impacts on the land and water. After the logging and farming bust, there was a push to promote tourism, which resulted in the building of seasonal cottages around many lakes. These early cottages were generally small, with few lawns, and had little impact on the lake’s nutrient levels. While habitat alteration undoubtedly occurred, it was not readily apparent through sediment core research. During the last few decades, there has been a large influx of people to the northwoods. Many seasonal cottages have been replaced by larger, permanent, year-round homes. Lawn care is much more intensive, and housing density around lakes has greatly increased.

These recent developments have led to large changes in shoreland habitat. Downed trees, which provide important habitat for the fish and insect communities, are often removed. Shoreline vegetation has undergone large scale removal or alterations, resulting in alarming declines in amphibians and changes in the bird community. Out in the middle of the lake, there have also been major changes in habitat. Prior to redevelopment and increased housing density, the plant community in many lakes consisted of low growing plants in low densities. With increased development came a shift to larger and denser plant communities. Sediment cores have almost universally shown this change. Recent studies by Dr. Susan Borman have verified this trend.

Dr. Borman examined plant records from the 1930s (seasonal cottages) and compared them to present day plant communities. She documented large changes in the plant community from low growing, sparse species to those that grow closer to the surface and are much more dense. Interestingly, cores taken from lakes without development do not exhibit a change in the plant community.

Sediment cores clearly show that Wisconsin lakes have undergone many changes during the last 150 years. Early colonization resulted in small increases in nutrients and large changes in habitat, specifically in the flourishing vascular plant community. Beginning in the 1940s, changes in our society and agricultural practices resulted in large increases in sediment and nutrient delivery to lakes. Thanks to soil conservation practices, soil erosion rates have generally declined during the last four decades. However, nutrient delivery has continued to increase because of the use of synthetic fertilizers. Shoreline development has also resulted in habitat alteration in the lake, and aquatic plant communities have been changed. Time has made it clear that what we do on the land will determine what happens to our lakes. With our history of unintended consequences, are we finally learning to plan ahead?