Field Notes—

Vernal Pools:

The Ephemeral Cradles Of Spring

By Curtiss Clark

When ice relaxes into water, the world quickens and flows. That shape-shifting sprite, H2O, is busy at this time of year appearing everywhere in every guise — solid, liquid, and vapor — awakening the world with all its sudden activity.

We associate these water-induced awakenings with spring, but there was a time 10,000 years ago when there was one great awakening after an era of ice when spring failed to show up for thousands of years. When the Laurentide Ice Sheet finally loosened its cold grip on Connecticut a hundred centuries ago and melted into runoff, the transformed landscape was revealed. The hills and vales had been sculpted by the solid scrape of ice into the terrain that now defines our home state.

Great quantities of ice had been ground into the soil, and when the ice melted the soil collapsed into depressions. Some of the larger depressions filled with water and became lakes and ponds along the emerging networks of coursing water. The smaller depressions, discrete and removed from the flow, survive only as ephemeral water bodies, capturing the snowmelt and spring showers in the months of March and April, then drying up in the summer heat, and sometimes reappearing in a rainy fall.

These temporary puddles, known as vernal pools, can be the size of a football field or the size of a tabletop, and because the water comes and goes, there are no fish. Consequently, vernal pools provide an ecosystem that is quite secure and comfortable for invertebrate fish food like snails, water beetles, and dragonfly and damselfly nymphs, and for amphibians like wood frogs and salamanders, which as tadpoles and larvae are vulnerable to fish predation.

Salamanders in particular are dependent on vernal pools for breeding. As adults, they return year after year to the same pool for their mating rituals. If you venture out of the comfort of your own preferred habitat on the first warm and rainy night in April to the slippery slop of the nearest vernal pool, you may be privileged to witness mass salamander courtship on a scale and of an intensity that would make a libertine blush.

The great salamander surge toward vernal pools on The Big Night sadly leads to mass slaughter if a busy road intervenes between these amphibians and their favored mosh pit. Their flattened bodies on the roadway the morning after are just one manifestation of the threat that development imposes on species that depend on these temporary teeming centers of woodland life and rebirth.

Because they dry up and disappear for long periods during the year, vernal pools are often overlooked and inadvertently destroyed when development quickly overtakes the terrain. They often exist in areas far away from watercourses, and consequently are not always afforded the protections they deserve as temporary, though vital, wetlands.

Without them, however, country life would not be the same — no spring peepers shouting down the cold quietude of winter, no glittering dragonflies stitching up summer afternoons, no twitching, splashing, life-laden oases calling unusual and beautiful migratory birds to our woodlands between seasons.

By definition, vernal pools are short-lived, but their continued existence, however brief, has a lot to do with the permanence of life in this corner of the world. It’s in our own best interests to do whatever we must to ensure they keep coming back.