The Drought

If you live in New England, you are well aware that we are in the midst of one of the worst droughts in decades. Where I live in northeastern Massachusetts, we just set the record for the lowest rainfall in recorded history between June and August (under 4 inches), which has been amplified by a historically dry spring.  Since January 2015, we are 18” behind where we should be in terms of precipitation. And the long-range forecast is not promising: meteorologists are predicting a warm and dry September and the potentially beneficial rains of Tropical Storm/Hurricane Hermine never materialized.

How will this drought affect our local ecosystems? It’s hard to say. Resilience is the term ecologists use to describe how quickly ecosystems can bounce back from catastrophic events. The resilience of a particular ecosystem is generally determined by the health of the ecosystem along with its level of biodiversity.  Areas with a wide variety of healthy plant and animal populations tend to be more resilient; any one catastrophe is unlikely to provide a fatal blow as some species will inevitably survive based on their unique set of traits. For example, a hurricane might knock down all the mature oak and pine trees in a Massachusetts forest, but the sun-loving trees that have been held in check in the forest understory such as beeches, cherries, and maples will soon grow and replace the damaged forest canopy.  Such a forest would exhibit excellent resiliency.  However if a forest has a compromised understory and contains trees that have been previously damaged by disease, human interference, or drought, the forest might take much longer to recover from hurricane-inflicted damage.

Our current drought is bordering the catastrophic and will put our local ecosystems’ resilience to the test. For the most part, our native plants will survive this drought. If we were facing multiple years of drought I’d be more concerned, but our native species are genetically wired to survive these tough times. Leaves will fall earlier (and probably won’t have as robust colors), the fall flowers will be fewer, and we may see a decrease in the nut and berry crop. But the vast majority trees and plants we see around us today will survive the winter and rebound in the spring (provided the drought doesn’t persist).

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An oak completely defoliated by gypsy moth caterpillars.

There are a few exceptions. Due to our dry spring, a certain species of fungus that infects gypsy moth caterpillars did not appear. We, therefore, experienced a population boom of these caterpillars and they effectively defoliated large swaths of mature oak forest. With severely damaged leaves, these trees could not photosynthesize at their usual rate and thus these trees have been weakened. This makes them more susceptible to disease and drought and it could be that some of these trees will not survive the winter. If we do experience large diebacks of our mature trees, it may take a while for our forests to recover. Much of our forest understory has been destroyed by an overpopulation of deer and an increase of invasive species such as common and glossy buckthorn. Without our native understory trees to replace the mature oaks favored by gypsy moth caterpillars, there could be significant changes to some local forests.
For most of our terrestrial animals, hot, dry summer is no different than a tough winter: it’s difficult and certain populations will dip, but it’s not a catastrophe. Animals have to work a little harder to find water (chipmunks for example like to raid vegetable gardens for fruits with high water content like tomatoes and squashes) and typical fall foods (berries, acorns, fruit) may not be readily available.
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The water in this pond usually covers the tube pictured here.

However, for our aquatic animals, this summer will be potentially catastrophic.  Most shallow or small wetlands in our area are completely dry. Rivers and ponds are well below their normal levels and warmer than usual. This leads to decreased dissolved oxygen levels that put even more pressure on our aquatic organisms. Frogs, salamanders, and turtles which depend on these habitats to survive are forced to wander great distances and often don’t survive the journey. Vernal pools have dried more rapidly than normal stranding frog and salamander larva that were unable to mature before losing the water they need to breathe. Our native cold-water fish such as brook trout, creek chubsucker, and fallfish will also be starved of oxygen as river waters slow, dry-up, and warm. These animals, whose numbers were already low due to disappearing habitat, could soon disappear from our local waters.

Unfortunately, humans place undue burden on our local ecosystems and reduce their resilience. The eradication of large predators has led to the robust deer population that has severely damaged our forest understory. We draw our drinking water from local wetlands and watersheds exacerbating drought conditions. There are only so many stressors our ecosystems can handle before they begin to fall apart.

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This shallow wetland has been dry for months.

Luckily, we are taking steps to lessen our impact. While further coordination is needed, all towns in Massachusetts are mandated to impose water-use restrictions when water is limited. Certain dams are being removed along our rivers, which will allow water to flow swiftly, thereby increasing oxygen levels and providing habitat for our cold-water fish. And unwittingly, by creating subdivisions and maintaining yards we are providing ideal habitat for eastern coyotes that seem to have developed a taste for white-tailed deer. Slowly but surely, we are beginning to restore resilience to our local habitats.
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