As California confronts its worst drought in a millennium, illegal marijuana operations are sucking up more and more of the water supply, leaving some of the state's wildlife high and dry. A new study from biologists suggests that illegal pot growing could put aquatic creatures like the steelhead trout and the already endangered coho salmon at risk.

“Clearly, water demands for the existing level of marijuana cultivation in many Northern California watersheds are unsustainable and are likely contributing to the decline of sensitive aquatic species in the region,” reads the study, published last week in the online scientific journal, PLOS One.

Researchers visited 32 marijuana greenhouses in the region, which is classified as one of the most biologically diverse in the world but is currently in a “critical” state, according to the World Wildlife Foundation. Last year, one of the study’s authors, biologist Scott Bauer, told Mother Jones magazine that marijuana farms are worse than logging and urban development in their damage to the environment.

California is in the midst of a record-breaking drought, possibly due to climate change. Farmers of all kinds are reporting that crop yields are down as much as 66 percent in just two years, and state officials declared a state of emergency in January to help cope with its devastating effects.

Medical marijuana has been legal in California since 1996, but the state still outlaws recreational growing and consumption. But illegal “trespass grows” continue to thrive in many of the state’s supposedly protected forests.

The researchers determined that every marijuana plant requires roughly six gallons of water per day. And based on their estimate that there are roughly 112,000 plants in the area they studied, they determined that the growing operations required about 673,000 gallons every 24 hours. If cultivation continues at this rate, it could reduce flow through local watersheds by 23 percent, according to the study. This is a big problem for endangered species such as coho salmon that badly need it.

“Given the specter of climate change-induced more severe and prolonged droughts and diminished summer stream flows in the region, continued diversions at a rate necessary to support the current scale of marijuana cultivation in Northern California could be catastrophic for aquatic species,” the study reads. “The extent of potential environmental impacts in these watersheds is especially troubling given the region is a recognized biodiversity hotspot.”