70 people were arrested yesterday in front of the White House in the first day of a 14-day-long protest against the building of a pipeline to the tar sands of Alberta, Canada. More will be arrested every day.

The 14 days of protest follows the delivery of a letter to President Barack Obama signed by 20 prominent climate scientists. The letter reads:

President Obama,

We are researchers at work on the science of climate change and allied fields. We are writing to add our voices to the indigenous leaders, religious leaders, and environmentalists calling on you to block the proposed Keystone XL Pipeline from Canada’s tar sands.

The tar sands are a huge pool of carbon, but one that does not make sense to exploit. It takes a lot of energy to extract and refine this resource into useable fuel, and the mining is environmentally destructive. Adding this on top of conventional fossil fuels will leave our children and grandchildren a climate system with consequences that are out of their control. It makes no sense to build a pipeline system that would practically guarantee extensive exploitation of this resource.

When other huge oil fields or coal mines were opened in the past, we knew much less about the damage that the carbon they contained would do to the Earth’s climate system and to its oceans. Now that we do know, it’s imperative that we move quickly to alternate forms of energy—and that we leave the tar sands in the ground. We hope those so inclined will join protests scheduled for August and described at tarsandsaction.org.

If the pipeline is to be built, you as president have to declare that it is “in the national interest.” As scientists, speaking for ourselves and not for any of our institutions, we can say categorically that it’s not only not in the national interest, it’s also not in the planet’s best interest.

The protest is a meticulously planned affair, conducted with practice and explicit agreement by all participants to “utterly peaceful” conduct.

To learn more, visit tarsandsaction.org.

Watch for more arrests today.