Concern about the environment is intensifying, but new efforts to reduce pollution and save energy differ from past environmental movements. Unable to get much satisfaction from the Republican-dominated federal government, environmental activists have set their sights on businesses — trying to influence corporate behavior and even forming partnerships with companies to confront environmental challenges. A growing number of businesses — including Wal-Mart, the world's biggest retailer — are concluding that saving the environment is good for the bottom line. But some conservative critics charge that such actions actually dilute companies' primary purpose — to increase shareholder value. Meanwhile, in the absence of federal action, state and local governments are instituting policies aimed at weaning industry from fossil fuels. And some environmentalists are even rethinking nuclear power.