In the U.S., one square foot of indoor marijuana cultivation uses four times more energy than the same space in a hospital, eight times more energy than a commercial building, and 20 times more energy than a center for religious worship, according to a study by Lewis and Clark College.

But a rising number of people in the fast-growing cannabis industry are trying to reduce their environmental footprint, from energy to water to pesticides. Still, a lack of research and regulation has left an industry that is on track to post $20.2 billion in sales by 2021 in a tough position. (Learn about the science of weed.)

In National Geographic magazine’s June 2015 edition, Editor-In-Chief Susan Goldberg wrote about the growing number of states that had legalized marijuana for medicinal and recreational use. At the time, less than half of the states in the U.S. had legalized the substance for medical use. Now, medical marijuana use is legal in 29 states and the District of Columbia.

Despite that expansion, this line by Goldberg still remains relevant: “The disconnect between the willingness of some states to regulate, sell, and tax marijuana and the federal reluctance to allow research to progress leaves an increasing number of people without the knowledge to make informed, science-based choices.”

Click to read the entire article on National Geographic.