Tennessee has an incredible abundance of plant and animal species due to its variable topography and climate and its plentiful caves and aquatic habitats.25 Tennessee’s natural systems have high levels of ecological importance but are subjected to pressures arising from climate change, land-use changes, and invasive species. For example, all unprotected eastern hemlock trees are expected to succumb to the spread of a nonnative insect, the hemlock woolly adelgid, over the next few decades as rising temperatures allow the pest to spread northward.26 The State’s natural resources are perhaps best explored by first examining land and its uses and then exploring the State’s water resources.
Tennessee’s urban and suburban areas have expanded in recent years, thereby causing the total amount of land allocated to forests and agricultural production to decline. Population growth and urbanization have affected current land-use patterns dramatically, and these changes are projected to intensify over the next several decades.27
The amount of forested land in Tennessee has generally been on the rise since the last century when many of trees were harvested for railroads and the land was put temporarily into agriculture. Today, most of the forested areas are natural second growth stands with less than 4% of Tennessee forests being plantations. In the early part of the twenty-first century, about 69% of forest land was in private ownership by individuals, 10% was owned by the forestry industry, and 13% was under federal or State government.28 However these numbers have been rapidly changing. Largely as a result of poor forest management, a recent widespread outbreak of the native southern pine bark beetle destroyed many pine stands.29 Combined with the pressure for land development for residential use, the number of landowners is increasing dramatically and average tract size is declining. Since 2008, much of the forested land in the Cumberland Mountains was sold as the market for wood moved overseas.30 Much of the large private forest land has become second home development (especially on the Cumberland Plateau).31
Agricultural land is an important component of Tennessee’s landscape. The total Tennessee area allocated to field crops in 2011 was 4.897 million acres. The top uses of that land were hay (1.880 million acres), soybeans (1.3 million), corn (0.8 million acres), cotton (0.5 million acres) and wheat (0.4 million acres).32 This allocation of land use responds to a large extent to the relative profitability of each activity, which is in turn impacted by changes in prices, cost of production, and yields.
The Tennessee River Valley has one of most biologically diverse fisheries and mussel populations in the world with many unique species are only found in this region.33 These aquatic populations can only be maintained with adequate stream flows and good water quality. Tennesseans have an ongoing need to balance increased water demand (from population growth and agriculture/industry) with water supply (from variable precipitation, slowly replenished groundwater resources and engineered storage systems).
Except for a small area east of Chattanooga, Tennessee lies entirely within the Mississippi River watershed (Figure 3). Westernmost Tennessee is drained by several small rivers directly into the Mississippi River. The rest of the State drains either into the Cumberland or Tennessee Rivers, both of which flow northward near the end of their courses to join the Ohio River along the Kentucky-Illinois border. The Tennessee River is formed by the juncture of the Holston and French Broad rivers at Knoxville. Other important Tennessee rivers include the Clinch, Little Tennessee, Hiawassee, Elk, Duck and Harpeth Rivers. Tennessee’s streams exhibit seasonal flow, with a pronounced peak flow in the spring and lowest flow rates in the fall. Natural stream flow has been obscured by the dams which have been constructed along all of Tennessee’s major rivers.
Hydrologic regions of Tennessee. Source: Webbers (2003) Public Water-Supply Systems and Associated Water Use in Tennessee, 2000. U.S. Geologic Survey.
Currently, most of Tennessee has ample surface and ground water resources to meet the demand of its population and economic sectors.35 Total available water storage from Tennessee’s combined surface and ground water systems is estimated to be 200 trillion gallons.36 In comparison, in 2005, total water use was approximately 10.6 billion gallons, with 82% for non-consumptive thermoelectric cooling water.37Annual use of water resources in Tennessee is therefore less than 0.005% of the total estimate of stored water in the State.
Surface, ground, and total water use by public water supply in Tennessee, 1950-2000. Source: Webbers and Ank (2003) Ground water use by public water supply systems in Tennessee, 2000. U.S. Geologic Survey.
Ground water is available in differing quantities across the State and in different types of aquifers (Figure 6). In eastern Tennessee, small quantities of ground water are withdrawn from wells or obtained from springs. Ground water is obtained from karst (cave and cavern) systems within central Tennessee. The most extensive ground-water resources, however, are present in unconsolidated and semi-consolidated sand and gravel aquifers in western Tennessee.
Principal aquifers and ground-water withdrawal totals for 2000. Source: Webbers and Ank (2003) Ground water use by public water supply systems in Tennessee, 2000. U.S. Geologic Survey.