Cheatham Reservoir faces dangerously low oxygen as summer approaches
July 13, 2026
Water temperatures at Cheatham Reservoir are already pushing 24°C, and dissolved oxygen levels are hovering near the minimum threshold for fish survival — all before the true heat of summer arrives. The federally impaired reservoir is stratifying as it warms, with deep layers becoming anoxic as the water column separates into warm surface and cold, oxygen-starved depths.Four separate segments of the system remain impaired under federal water-quality standards, yet cleanup plans exist for only one of them. The fragility of this water body traces directly to its design: the dam that created the reservoir in 1952 locked in the physics of thermal stratification, a dynamic that intensifies every summer and leaves the deeper waters unable to support life. As conditions deteriorate further in the coming months, fish and other aquatic organisms will have shrinking refugia.
Monarchs and milkweed in midsummer
June 7, 2026
The air shimmers with heat over the meadows near downtown Nashville, where summer has settled into its longest days. Common milkweed stands shoulder-high in scattered patches, their broad leaves catching the morning light before the temperature climbs. Each plant holds a cluster of dusty pink flowers at its crown, releasing a sweetness that carries on the still air.A monarch butterfly works methodically through the milkweed patch, her orange wings marked with black veins and white-spotted borders. She is not here for nectar. The female monarch tests each plant with her feet, drumming against the leaves to taste the chemistry beneath. When she finds the right plant, she curves her abdomen and places a single cream-colored egg on the underside of a young leaf. The egg is smaller than a pinhead, ribbed like a tiny melon. She moves to the next plant and repeats the process, spacing her eggs carefully across the patch.The milkweed she chooses will be both nursery and food for her offspring. When the caterpillar hatches in three days, it will eat its own eggshell first, then begin consuming the milkweed leaf. The plant's milky sap contains cardiac glycosides, compounds toxic to most animals but harmless to monarch caterpillars. As the caterpillar feeds and grows through five molts over two weeks, these toxins accumulate in its tissues. The bright yellow, black, and white stripes that develop serve as a warning to predators: this caterpillar tastes terrible and could make you sick.The milkweed tolerates this relationship. A single plant can support several caterpillars without significant damage, and the adult monarchs that emerge will visit other milkweed patches for nectar, carrying pollen between plants. The monarch's dependence runs deeper than convenience. No other plant can substitute for milkweed in the caterpillar's diet. Without milkweed, there are no monarchs. In Nashville's urban landscape, where development fragments natural areas, these patches of common milkweed become islands of possibility. The female monarch may have traveled miles to find this stand, following chemical cues and visual landmarks that guide her to the plants her species requires. Her eggs represent the continuation of a journey that began in Mexico and will end in Canada, carried forward by successive generations that live and die without seeing the same landscape twice.The milkweed flowers release their fragrance strongest in the early morning, before the heat builds and the air grows still. If you find yourself near a patch like this one, notice how the sweetness carries just a few feet before dissipating, drawing you closer to see what the monarchs have found.
Swallows gather insects over Shelby Bottoms water
May 23, 2026
The air above Walter S. Davis Boulevard Marsh shimmers with movement. Tree swallows and barn swallows cut precise arcs through the warming air, their wings catching the late spring light as they work the space between water and sky. The Cumberland River bottomland spreads wide here at Shelby Bottoms, and the marsh holds the morning coolness even as the day builds heat.Both swallow species arrive at this same airspace for the same reason: insects are lifting off the water in steady pulses. Midges, mayflies, and caddisflies complete their aquatic larval stages and emerge as winged adults, rising from the marsh surface in loose clouds. The tree swallows take the higher hunting lanes, their iridescent blue-green backs flashing as they bank and turn. Barn swallows work closer to the water, their deeply forked tails acting as rudders for tight maneuvers around the cattails and emergent vegetation. Each species has carved out its feeding territory in three dimensions.The timing is precise. These aquatic insects have spent months or even a full year developing in the marsh sediments and shallows. As water temperatures climb and daylight stretches longer, they emerge in synchronized waves. The swallows have timed their own nesting cycle to match this abundance. Tree swallows nest in the wooden boxes and natural cavities around the marsh edges, while barn swallows construct their mud cups under the nearby bridges and building overhangs. Both species are feeding young now, and a single brood requires thousands of insects over the course of two weeks.The swallows' hunting techniques reveal the insects' behavior. Tree swallows climb and dive in loose spirals, following the thermal currents that carry insects upward from the warming water surface. Barn swallows skim and dart just above the marsh grass, intercepting insects before they gain altitude. Each swallow can catch and swallow an insect every few seconds during peak emergence periods. They return to their nests with their throats bulging with compressed prey, then immediately return to the hunt. The red-winged blackbirds call from the cattail stands below, and the green heron waits motionless at the water's edge, but this aerial feast belongs to the swallows.The marsh surface reflects the morning sky, broken by the expanding rings where insects push through the surface tension. Somewhere above, a swallow banks into another turn, its shadow racing across the water before disappearing into the light.
