For years now I have argued that it is time to retire the old “canary in a coal mine” metaphor about early signals of the effects of climate change and other environmental problems.

Well, here’s a phrase that could potentially replace it: “the damselfly in the river.”

Maybe that doesn’t quite have the same ring to it. Nevertheless, it’s clear that damselfly species around the world are suffering. At least 24 percent of the colorful, dragonfly-like insects are currently threatened with extinction, and according to newly published research, their deaths could be just as much a harbinger of things to come as those of the proverbial canaries.

Damselflies rely on freshwater for their survival. They breed in freshwater and most species stick pretty close to the places where they hatch—a problem in a world where freshwater resources are becoming increasingly scarce. Declining damselfly populations, therefore, could be an indication of water shortages to come.

Take northern Africa, for example. According to a paper published May 5 in the International Journal of Odonatology—that’s the study of damselflies and dragonflies—north Africa is one of the most water-scarce places on Earth, “with one half of the population living under conditions of water stress and the per capita water availability expected to halve by 2050.” Climate change will cause about 22 percent of those future water shortages. The rest will be caused by socioeconomic factors such as a rapidly increasing human population and the need to feed and support all of those people.

The damselfly species that was once widespread in northern Africa—southern damselflies (Coenagrion mercuriale)—will not handle those water stresses well. The paper—by a team of researchers from six countries—found that species has disappeared from all but one of its habitats in Tunisia (including Dougga, a World Heritage site) and 45 percent of their habitats in Morocco. Most of the damselfly’s decline has taken place since the turn of the 21st century, and some populations have disappeared in just the past five years. The remaining populations have become increasingly fragmented and face declining numbers that indicate they may also be dying off.

The main cause of the decline, the researchers found, was human exploitation and diversion of rivers to irrigate nearby land or villages. Lowland habitats were hit the worst by far. In fact, 95 percent of the remaining damselfly populations exist at altitudes of 1,500 meters or more, places humans are less likely to tread. All low-altitude sites in Morocco are devoid of damselflies, according to the paper.

The southern damselfly’s demise has been a long time coming. The researchers tapped into records dating back more than a century and documented the slow but sure conversion of habitat from seminatural rangeland to crops to, most recently, villages. Each step along the way required more water.

And change is still coming. In addition to fruit and vegetable crops, the researchers found that cannabis, “once traditional and restricted to certain areas...has expanded, and large areas in the north of Morocco are now being used for its production.” Cannabis crops have taken over areas previously devoted to food production, and the traditional dry-climate Kif variety is being replaced by water-hungry hybrid plants that have already made water in the region scarcer.

The researchers only found a single, solitary damselfly in the mountainous Rif region of Morocco where most of the cannabis production takes place. Maybe high-altitude sites aren’t so safe after all.

What comes next? The researchers wrote that more studies are needed to understand the southern damselfly’s habitat needs and jump-start conservation. Meanwhile, we also need to learn how water shortages are affecting, and will affect, all the other flora and fauna in the region.

Humans, as you might guess, are on that list.

“Damselfly in the river,” indeed.