Northern Blackland Prairie

Austin Camp Mabry, 6 km from Northern Blackland Prairie, recorded mean daily high of 101.8°F over the past 30 days, 8.2°F above the normal of 93.6°F for these calendar days. The warmest day reached 107°F on August 22, combining with the deficit rainfall to drive drought intensification and reduce streamflow.

September 2025 brought 0.5 in of precipitation to Travis County, 2.7 in below the 1901-2000 normal of 3.2 in, ranking it the 9th driest September in 131 years of record. Current conditions show month-to-date rainfall of 0.1 in, 1.8 in below normal by September 21, extending a pattern of exceptional seasonal dryness.

Guadalupe Bass (listed as Threatened on iNaturalist) were observed on 2026-09-18 in Bull Creek and 2026-09-03 near Bull Creek; Greenthroat Darter (Threatened) was documented on 2026-09-11 at Lost Creek Boulevard, Austin. Both species are endemic to Texas streams and require flowing, clear water habitats that drought and flow alteration threaten.

Severe drought conditions (D2 or worse) expanded from 10.35% to 35.27% of Travis County between early September and the week of 2026-09-15 to 2026-09-21. The rapid worsening of drought stress concentrates pollutants in reduced streamflow and warms water, limiting the dissolved oxygen availability that freshwater organisms depend on.

Barton Springs salamander, an endangered species found only in Barton Springs habitat in Austin, was recorded on 2026-09-09. This tiny lungless salamander depends on cool spring water and is confined to its single spring system; worsening drought stress on regional groundwater poses an ongoing threat to its survival.

Travis County's drought picture looks dramatically better than it did in January, when extreme-to-exceptional conditions blanketed the entire county and severe-or-worse coverage stayed pinned near 100 percent all the way through early June. Since then the numbers have fallen fast: severe drought coverage dropped to about 66 percent by late June, then to roughly 16 percent through July, and now sits just above 10 percent, with no part of the county rated extreme or exceptional. At the county scale, that is a genuine recovery. But the map's green doesn't match what the water is doing at Barton Springs. Two weeks ago, streamflow on Barton Creek above the springs had dropped to near zero, and dissolved oxygen had fallen to 4.9 milligrams per liter, a level at which fish and aquatic insects start to feel real metabolic stress. Almost the entire county is still classified as abnormally dry, and nearly two-thirds remains in moderate drought, so the underlying dryness hasn't actually left, it has just eased out of the most severe categories. Spring-fed systems like this one often run on a different clock than the surrounding land, since Barton Springs draws on the Edwards Aquifer. Whatever the exact mechanism, the pattern here is clear: the county's drought index is improving, but the creek above the springs is still running low and short on oxygen, a local hotspot that isn't tracking the broader rebound.

Dissolved oxygen at Barton Springs has fallen to 4.9 mg/L — a threshold where most aquatic life begins to feel real metabolic stress. The cause is straightforward: streamflow at Barton Creek above Barton Springs has dropped to near zero, briefly touching zero in the past week, and tributary gauges across the city show similarly low conditions. Still water in summer heat cannot hold as much oxygen as moving water does, and when the springs slow to a trickle, the oxygen buffer that usually sustains this system shrinks with it. Water lettuce (Pistia stratiotes), which iNaturalist tags as threatened and native — a classification that is itself contested, as the plant is widely regarded in Texas as an introduced aquatic weed — has been observed consistently along Lady Bird Lake and the Butler Trail corridor since last summer. Its dense mats shade the water surface and block wind-driven mixing, conditions that can further depress oxygen in slow-moving pools. The combination of reduced flow, high summer temperatures, and floating surface cover creates a cascade of oxygen depletion worth watching closely over the coming weeks. The endemic aquatic species of Barton Springs — most critically the salamander that bears the springs' name — have evolved in an environment of cold, constant flow. They have virtually no margin for error when oxygen margins get this thin.

The creek ran dry this week. A month ago, flow measured 165 cubic feet per second — a modest but steady pulse through the summer channel. Now the gauge reads zero, and the aquifer springs that feed these karst streams have stopped flowing. When flow ceases, aquatic life has nowhere to go but the remaining pools. Fish, invertebrates, and plants compress into shrinking refuge pools where July heat climbs toward 100°F and oxygen crashes. These congested refuges become ecological traps — temporary, stressed, unsustainable. The creek's impaired waters listing exists precisely for moments like this, when the system can no longer support the life it normally carries. Karst streams in summer depend entirely on springs. Once the aquifer stops delivering water, collapse comes fast.

American beautyberry is flowering across the creek corridors this week, a rare splash of blooms pushing through the peak heat of June. With over 50 sightings documented along the greenbelts in just one week, the native shrub is in full stride — timing that matters. Summer is a lean season for nectar-feeding insects here; most spring bloomers have faded and fall flowers haven't begun. Beautyberry fills that gap, drawing bees and butterflies when they need it most. In two months, those flowers will give way to the plant's namesake magenta berries, food for indigo buntings, cardinals, and other southbound migrants stocking up before their journey. This is native plants working the way they evolved — not a flash display, but a carefully timed offering that threads the seasons together.

Along the rocky slopes and cedar edges near Austin, snake apple vines are climbing whatever they can find right now. The stems are thin and wiry, the leaves deeply lobed, and the small yellow-green fruits hang where flowers were a few weeks ago. It is easy to walk past this plant without stopping. But look closely at the undersides of the leaves, and in early summer you may find what you are looking for: small clusters of rust-orange eggs, each one the size of a pinhead, laid in tight groups by the pipevine swallowtail. The pipevine swallowtail is a large butterfly, dark-winged with an iridescent blue-green sheen on the hindwings that catches the light when it moves through dappled shade. The adults nectar widely, visiting wax mallow and other open flowers in the heat of the day. But for laying eggs, the female is specific. She seeks out snake apple, and a handful of other native pipevines in the region, because the plant contains aristolochic acids, a group of compounds that are toxic to most insects and to vertebrates. The caterpillars that hatch from those orange eggs are not harmed by these compounds. Instead, they eat the leaves and incorporate the acids into their own tissues. The caterpillars start small and dark, almost black, with rows of fleshy orange tubercles along their backs. As they grow through their instars, the color intensifies. By the time they are fully grown, they are conspicuous: dark brown to reddish-black, those orange knobs prominent, the body thick and slow-moving on the vine. This is not camouflage. The coloration is a signal. Birds that have tried eating one of these caterpillars, or the adult butterflies that emerge from them, learn the association. The bright colors and the bad taste reinforce each other. A blue jay that samples a pipevine swallowtail larva once tends not to try again. What makes this relationship ecologically interesting is how it extends beyond the two species directly involved. Several other butterfly species in this region, including the red-spotted purple and certain female tiger swallowtails, have wing patterns that closely resemble the adult pipevine swallowtail. They do not carry the aristolochic acids themselves, but they benefit from the learned aversion that predators have developed toward the pipevine's coloration. The pipevine swallowtail is the anchor of that mimicry system, and the anchor depends entirely on snake apple being present in the landscape. Snake apple is a native vine of the Texas Hill Country and the Edwards Plateau, well adapted to thin limestone soils and summer drought. It dies back to a tuberous root in winter and leafs out again in spring, which is why the pipevine swallowtail's egg-laying tracks the vine's growing season so closely. The female butterfly is not simply finding a food source; she is finding the one plant whose chemistry her offspring can use. How she locates individual vines, which can be sparse and scattered across a landscape, is not fully resolved, but contact with the leaf surface appears to trigger the decision to lay. She lands, drums with her forelegs, and within seconds either moves on or begins depositing eggs. Right now, in the long days of early summer, the vines are in full leaf and the first egg clusters are appearing. If you find a snake apple vine and check the undersides of several leaves, you may find eggs, young larvae, or the characteristic feeding damage where a caterpillar has taken irregular bites from the blade. The caterpillars do not strip a plant bare; they move between leaves, and a healthy vine can support a small cohort without losing too much tissue. The relationship is close but not destructive, calibrated over a long association between this butterfly and the plants in this genus. The air near Austin is thick and warm by mid-morning now, and the light comes down hard through the cedar and oak. Somewhere in the scrubby edges, a pipevine swallowtail is working the understory, wings tilting as it moves from shade to sun and back again.