The Declaration of Independence is not technically a legal document. But even if we ignore that, it would still quite a stretch to go from a general right to life to a right to some particular environmental policy. It's unreasonable to expect the government to always take the course of action that prevents the most deaths (or else the government would be required to ban driving, unhealthy lifestyles, etc.) and once we accept that reasonable tradeoffs between "life" and other policy goals are acceptable then we must (IMO) concede that Congress (and agencies empowered by Congress) have the authority to make these tradeoffs except when there are specific Constitutional directives to the contrary.
I would go even further and argue that a policy intended to reduce global warming is not necessarily the one that best defends the right to life (or rather the American right to life) as opposed to a policy of burning more fossil fuels now in order to build a stronger foundation for American security in a world destabilized by global warming.