No issue facing us today has more catastrophic potential than man-made climate change, which is destined to make a large part of the Earth uninhabitable within our lifetimes unless we act now.

But our divided politics and a lack of trust in institutions have made it impossible for this country, which trails only China as the top emitter of heat-trapping greenhouse gases, from taking the kind of action that can hold off the worst effects. Until that changes, it’s up to states and regional organizations to do what they can to move us from burning carbon-emitting coal, oil and gas for power generation and transportation to, whenever possible, using renewable energy sources, like wind, solar and hydroelectric power.

Through that lens, we support the agreement signed by Gov. Mills and other stakeholders supporting New England Clean Energy Connect, a proposed transmission line between Canada and Maine that would enable Massachusetts to meet its renewable-energy goals by buying hydroelectric power from the company Hydro-Quebec.

The deal has been controversial, for good reason. In order to build the line, Avangrid, the parent company of Central Maine Power, would have to clear a corridor through commercial forest in central Maine that would be visible from some vantage points.

NO COST-FREE POWER

But there are costs associated with every kind of energy. New England has to prepare for the retirement of two nuclear power plants that will not be replaced in the current regulatory environment. The most likely type of generation to take their place would be new natural gas generation, which is cleaner than coal but still a fossil fuel that would contribute to climate change.

One way to see how complicated the trade-offs are is to look at the array of supporters who signed on to the deal Mills endorsed last week. In addition to her office of energy, you’ll find Public Advocate Barry Hobbins, who represents Maine ratepayer interests at the Public Utilities Commission, and environmentalists from the Conservation Law Foundation and Acadia Center.

The opponents’ lineup is also diverse, pairing the Natural Resources Council of Maine with the organization of power plant owners who don’t want to face competition from a government-subsidized competitor. There is also opposition from area businesses, residents and property owners, who object to the project’s visual impacts.

The most troubling concern is the question of whether this deal will result in any reduction of greenhouse-gas emissions. The Natural Resources Council has raised doubts about Hydro-Quebec’s ability to fulfill its obligation to Massachusetts and still be able to sell hydropower on the spot market to other utilities. If the company’s current customers are not going to be served, they will have to go elsewhere, likely to fossil fuel-burning outlets.

ADEQUATE CAPACITY

In response, Hydro-Quebec says it has the capacity now to meet all of its customers’ needs and it is adding capacity. The company says that it is currently “spilling” more than enough water without running it through its generators to meet the demand to Massachusetts. Regulators will have to confirm that before permitting this project.

But other critiques are easier to answer, particularly the claim that Maine would receive no benefits. Adding this much power to the grid, even if it has been bought by Massachusetts, will suppress prices here.

And in negotiations with the state, Avangrid commits to helping pay for electric vehicle charging stations, and conversion to highly efficient electric heat pumps for low-income households that heat with oil.

The new power line would create a visual impact, but climate change is a much greater danger to the forest ecology than a transmission line.

Creating a pathway for Canadian hydropower into northern New England is not all Maine should be doing to reduce its carbon footprint. It will still be important to increase the use of electricity for space heating and transportation, while generating more power from renewable sources, like solar and wind, both onshore and offshore.

As this project heads into its final phase, regulators should put climate impact on the top of their concerns and make their decisions accordingly.