They are definitely concerned in as much as environmental problems link to instability and loss of political capital. (See my writings on narratives of ecological civilisation for detailed discussion on this). In brief, solving environmental problems is (and always has been since imperial times) a fundamental part of governing China, and is crucial to Chinese leaders' legitimising their power. That said, there is a strong belief that environmental problems are largely solvable through technocratic means, thus pollution and species extinction and even climate change are just problems waiting for strong leadership to solve them, rather than signals of a true need for deep-rooted course correction (this is the mainstream view; there are exceptions from individual leaders seeing differently). Environmental goals are being pushed hard today by Xi as a means to increase centralisation of power and legitimise the increased role of the Party. This is not a grassroots environmentalism.