How pot industry affects the environment

First Colorado and Washington, then Oregon and Alaska, and now California. While other states have legalized marijuana use among adults, none of these states addressed the environmental toll that comes with cultivation of this increasingly lucrative crop. California now has an opportunity to reverse that trend.

Countries such as Uruguay, Morocco, and the Netherlands, as well as 23 U.S. states have decriminalized marijuana in some manner. While legalization and liberalization in other places has focused attention on the public health and criminal justice consequences of liberalization, the environmental harm associated with the commercial-scale cultivation of marijuana has been neglected.

Marijuana Canada Cannabis
Harriet Taylor | CNBC

In California, where the multi-billion dollar marijuana industry produces 60 percent or more of the marijuana consumed in the United States, forests, streams and wildlife have taken a hit from the impact of cultivation. As the legalization debate heats up, the environment must be part of the conversation.

The state legislature made progress on tackling environmental impacts this summer, but only for medical markets, and did not provide adequate funding to address the environment. A citizen-led legalization initiative filed on Monday – the Adult Use of Marijuana Act – takes policy efforts further and includes strong environmental provisions and dedicated funding to prevent, regulate and clean up environmental harms associated with this industry.

Marijuana is grown in the hidden corners of California, in undeveloped, remote watersheds that are also home to sensitive animals like endangered salmon, steelhead trout, and northern spotted owls. Marijuana growers often tap streams directly and take water exactly when fish need that water in streams. The California Department of Fish and Wildlife found that this type of irrigation can significantly reduce or even eliminate stream flow during California's dry season, particularly during drought years, threatening the survival of rare and endangered salmon, amphibians, and other animals.

Cultivation is also associated with unsanctioned forest clear cutting and road construction, which can dramatically increase erosion, destroy habitat, and damage streams. Marijuana plantations can also pollute lands and water, as well as poison wildlife through use of pesticides, herbicides, fertilizers, and petroleum fuels. For example, chemicals, used heavily in black market marijuana cultivation on public lands, such as national forests, have made their way into the food chain. These poisons pose significant risks to predators like the rare Pacific fisher and Northern spotted owl. Even where grown indoors, pot can require extensive energy inputs with potential negative effects on climate.

The Nature Conservancy, working with government resource agencies and stakeholders, has determined that in California it will take at least $25 million a year to adequately regulate the industry and enforce environmental laws; and more than $100 million per year for the first five years to clean up the environmental damage and restore impacted lands.

In the proposed ballot initiative for November 2016, 20 percent of sales and wholesale tax would be dedicated to environmental protection and restoration. We estimate this would generate enough revenue to address the environmental impact. And importantly, state resource agencies would have the necessary authority and funding to regulate marijuana cultivation and enforce existing environmental regulations, and cultivators would be required to comply with laws and regulations related to environmental impacts, natural resource protection, water quality, and water supply.

California stands at a crossroads and must ensure that the environment is considered in any marijuana policy that is adopted. If legalization were to happen without environmental protections, the problem could get much worse.

Commentary by Jennifer Carah, freshwater ecologist for The Nature Conservancy in California. She works on salmon habitat restoration and conservation projects, and was the lead author on a recent study on environmental impacts of marijuana cultivation entitled, "High Time for Conservation: Adding the Environment to the Debate on Marijuana Liberalization."