by Dr. Sarah Treanor Bois, PhD
Director of Research & Education at the Linda Loring Nature Foundation
All of Massachusetts is on some kind of drought status now as of this past weekend. Nantucket is still at a Level One which is considered a “mild drought.” We’re better off than much of the state, but it doesn’t mean we’re in the clear. Central and northeast regions of Massachusetts are in “Critical Drought” status. There is no meaningful rain in the forecast despite a few wet evenings. The hot temperatures continue and so will these conditions.
It’s not atypical for the Northeast to experience droughts in the summer; 2016 and 2020 both saw statewide drought conditions. According to Julia Blatt, Executive Director of the Massachusetts Rivers Alliance, even though the dry conditions usually only last for a few months, they can still have harmful effects on local ecosystems and water supplies. More frequent and severe droughts are expected as climate change continues to increase temperatures, raise evaporation rates, and dry out soils—even in spite of more precipitation and heavier rainfall events overall in our region.
The good news for our Nantucket habitats is that many plants and animals have evolved to live in our nutrient poor soils which drain quickly. Sandy soils and salty air make many species already adapted for drought-like or otherwise waterstressed conditions.
What happens to our plants in a drought?
Since plants can’t just pull up their roots and relocate to a shady or damp spot, they somehow need to deal with these ever-increasing drought conditions.
Some plants are drought-resistant; plants that can withstand dry conditions without dying. A drought-resistant plant can survive drought by using three defense strategies: escaping, avoiding, or tolerating water loss.
Succulents have thick fleshy leaves that store moisture, and they have a thick waxy layer to leaves and/or stems to prevent water loss. Our native prickly pear cactus (Opuntia humifusa) is a great example of this. You have to be pretty hearty to live in an extreme environment like Coatue.
The waxy coating on leaves of some plants not only prevents water loss, but also protects the plant from salt spray effects. Seaside goldenrod (Solidago sempervirens) is a great example of this. So is High Tide Bush or Groundsel (Baccharis halminifolia). Bayberry (Morella pensylvanica) is also in this category with nutlets that are waxy coated seeds rather than fleshy berries that will desiccate.
Most of the water a plant loses is lost due to a natural process called transpiration. Plants have little pores on the underside of their leaves called stomata. Plants will absorb water through their roots and release water as vapor into the air through these stomata. To survive in drought conditions, plants need to decrease transpiration to limit their water loss. Some plants that live in dry conditions have evolved to have smaller leaves and therefore fewer stomata. Other plants may completely shed their leaves in a drought, to prevent water loss. You can see this in action by color changes on the landscape. Fall hasn’t come early – some plants are just senescing or dropping leaves. The basic rule is that fewer leaves mean less water loss through transpiration.
Another way plants reduce water stress is by only opening their stomata for gas exchange during the evening instead of daytime, reducing transpiration. This means the plant may grow slower or appear wilted during the day since photosynthesis is limited. When stressed, the plants do what they have to in order to survive if not thrive!
For those plants where “escape” is a strategy, one option is to respond to drought by going to seed. Many seeds can withstand dry conditions for some time and germinate once there is moisture present again. Not an ideal option, but you may see some plants setting seed earlier in response to overly dry conditions.
While some of our native vegetation is drought tolerant or can likely survive due to adaptations from living in harsh environments, other habitats on-island may not fare so well. Some of our existing habitats like our red-maple swamps, beech forests, and other woodland habitats established during a time period when there was relatively ample water available. As a result, many species in these habitats are drought-intolerant, such as bats, salamanders, toads, freshwater fishes, and turtles. Consequently, these species and their supporting habitats depend on current seasonal water regimes and are highly vulnerable to changes in where, how, and when water is delivered.
There may also be other impacts to our ponds and aquatic systems. We may see increases in the number, size, and duration of harmful algal blooms (HABs). Reduced flow and water levels for our waterways including groundwater and surface water, can in turn affect aquatic life and habitats.
While it’s difficult to pinpoint this particular drought on climate change effects, looking at the data for the past few decades, the Northeast has experienced more summertime droughts in the last few years than is typical. In general, climate change is exacerbating our weather extremes; we’re seeing more precipitation during wet periods and longer durations with no precipitation during dry periods.
These dry conditions have also increased fire activity in the state. Drought induced fire behavior can result in suppression challenges for fire resources and result in extended incidents so residents are asked to exercise caution while working with open flames. Please remember this and use extreme caution with fires on-island.
Many Massachusetts communities have instituted water conservation measures limiting indoor and outdoor water use. These measures can include watering bans some with strict penalties. The state office of Energy and Environmental Affairs, which is in charge of declaring drought conditions, has released the following water use recommendations for residents and businesses.
Level 1 drought recommendations (where Nantucket is at now):
- Limit outdoor watering to 1 day a week, and only water between 5 p.m. and 9 a.m. when less water will be lost to evaporation.
- Consider switching to efficient toilets, faucets, and showers that use less water.
The restrictions only get more severe from there. The state’s website has more information on how to conserve water indoors and outdoors.
Now is when we can also start to do some long-term planning to make our homes and businesses more drought tolerant in the longer term. One thing you can do to help conserve water is to plant native. Native plants require overall less supplemental water since they are adapted to Nantucket soil and climatic conditions. Check out this local resource for ideas on planting Nantucket native: nantucketlandcouncil. org/wp-content/uploads/Biodiversity-Broch-Pages-In-order.pdf.
If you’d like to keep tabs on daily precipitation on Nantucket, the Linda Loring Nature Foundation and others collect daily rainfall data for the Community Collaborative Rain Hail and Snow Network (CoCoRaHS). You can see the daily reports for our island and region at https://maps.cocorahs.org/