If you haven’t noticed, Pennsylvania and New Jersey have been a bit dry. Most public parks and private landowners now have fire restrictions in place and some well-known streams and reservoirs are actually shriveling up. While the seemingly unending days of blue skies can be picturesque, there are unseen challenges to a long dry season.
According to the Department of Environmental Protection, the city and the surrounding regions are currently in a ‘drought watch.’ One of four stages — normal, watch, warning and emergency — a watch is intended to alert government agencies, suppliers, users and the general public to any growing conditions that might indicate the potential for future drought-related problems.
A drought watch is determined by consistent measurements and data collection on the groundwater levels (wells), surface water levels (streams) and precipitation levels (rain). So, even after a nice drenching downpour, if the other two indicators are below a certain range, the drought and all its restrictions can still be maintained.
The focus during a watch stage is on increased monitoring, awareness and preparation for a response if these dry conditions become worse. The people who are impacted can consider voluntary water conservation efforts — shorter showers, less laundry washing, accepting dry grass yards, opting out of the weekly car wash.
But what about the local ecosystems?
Drought conditions can cause first order streams — the smallest, unbranched waterways or headwaters — to cease flowing, deeply impacting freshwater environments. “The drying of streams and connected ponds could reduce the populations of critical amphibians,” says Ned Gilmore, collection manager of vertebrate zoology. “Especially species that are in their larva stage, when they are entirely dependent on being in water.” Pennsylvania is home to diverse populations of amphibians, including salamanders, frogs and toads, who all depend on freshwater resources.
“Furthermore, if those streams are not connected to larger tributaries or rivers, this drying up can impact the important macroinvertebrate larvae and nymphs, such as snails, crayfish, worms, who live in those particular streams,” explains Tanya Dapkey, Macroinvertebrate Section lead in the Patrick Center for Environmental Research. Macroinvertebrates play a foundational role in freshwater ecosystems by recycling nutrients, as well as being a necessary food source to larger creatures.
The location of the salt line in the Delaware River estuary is also determined by freshwater inputs from upstream. As the drought persists, less water moves downstream, and so the salt line creeps further up the estuary. Why does that matter? “Salinity is a major determinant of fish species distribution in estuaries,” notes David Keller, the Fisheries Section lead in the Patrick Center. “Each species has a preference and range of salinities that it can tolerate.”
So as the small waterways dry up and saltier waters from the Delaware Bay move upstream, less habitat is therefore available for aquatic life — amphibians, fish, macroinvertebrates and plants — that require freshwater for survival.
Adult amphibians and fishes and winged macroinvertebrates may be able to move to areas that remain saturated with freshwater. But for everyone else, the smaller animals, larvae and nymphs, the less tolerant fishes and rooted plants, if they don’t relocate fast enough or are simply stuck, they can perish in the dried stream bed or if salinities are too high for too long.
“Without a way to move quickly, or even with nowhere to go, these species can be locally extirpated,” Dapkey adds.
Droughts also affects insects at multiple levels. “Those feeding on trees in late summer and early fall, caterpillars for example, may have found the leaves wilting and prematurely dropping off. So it is likely many did not survive to complete feeding,” says Jon Gelhaus, Curator of Entomology.
He adds that soil insects very likely had to dig down deeper as the top soil layer got drier and harder. Leaf litter also became prematurely dry and so the usual fungal activity, which decomposes the leaves and insects feed on, likely stopped, resulting in certain mushrooms becoming nonexistent and insects loosing out on a food source.
For landlocked plants, the current drought watch has occurred during a relatively normal time to be dry: after the growing season. In other words, there isn’t much of a current impact on any plants, native or invasive, as they have finished the hard work of reproduction over the spring and summer.
“For the most part, these plants have already completed their evolutionary goal and produced fruits,” says Chelsea Smith, collection manager of the Botany Department. “Their seeds and any perennial plants will all be in dormancy over the late fall-winter season.”
She notes, however, that if drought conditions continue during this transition season over the next few years, or in other words, very dry autumns become the norm, that could absolutely impact seed viability and the long-term growth of perennial natives.
And if these dry spells in autumn continue across several years, it could also impact the other transition season — spring. “Vernal ponds, which usually fill with water in the spring, could stay dry all year around without enough groundwater and precipitation, thus preventing a whole year without any offspring,” Gilmore notes. This is especially detrimental for sensitive or endangered species in the state. Gelhaus also adds, “These declines for insects should carry into next year’s seasons due to reduced survival and oviposition in the fall.”
Academy scientists have been studying the ebbs and flows of water ecosystems for over two hundred years, including diatoms — microscopic algae found in water that contribute about a quarter of the oxygen we breath as a by-product of photosynthesis. “Diatom community composition definitely shifts during droughts due to increased surface evaporation in rivers and lakes, which raises mineral concentrations in the water,” says Laura Aycock, collection manager of the Academy’s Diatom Herbarium. “Diatoms are highly sensitive to these changes.”
A single dry autumn might seem like simply a nuisance or an ongoing news headline, but it can have rippling effects for many species, small and big, far into the future. So, what can we do?
“Follow guidelines,” states Dapkey. Simply reducing your water usage and restricting burns and fires can go a long way to supporting your community through drought watches. But these measures also significantly help the local ecosystem, and all the species of life that depend on it, too.
I’ve been concerned about the drought effects on wildlife in my area. I’m sure the drought will have an effect on many larger animals as well. We have been trying to conserve water and following the burn ban restrictions. We live in a watershed area and the damage from lack of rain is painfully obvious.