The Supreme Court heard five environmental law cases in the term that ended Monday, and environmental groups lost every time. It was, said Richard J. Lazarus, a director of the Supreme Court Institute at Georgetown University Law Center, “the worst term ever” for environmental interests.

The court allowed Navy exercises using sonar that threatened whales off California. It limited the liability of companies partly responsible for toxic spills. It made it harder to challenge Forest Service regulations and easier to dump mining waste into an Alaskan lake. And it allowed the Environmental Protection Agency to use cost-benefit analysis to decide how much marine life may be killed by cooling structures at power plants.

Business groups expressed measured satisfaction with the decisions.

“The court does seem to be bringing more common sense back to environmental law,” Robin S. Conrad, a lawyer with the United States Chamber of Commerce, said at a recent news briefing.

In the past 40 years or so, ever since environmental law emerged as a separate field based on major statutes enacted in the 1970s, the Supreme Court has been reasonably receptive to cases brought by environmental groups.

That seems to have changed under the court of Chief Justice John G. Roberts Jr.

“It has taken a little while, but we are finally seeing how much the changes in 2005 and 2006 moved the court in important areas, including in environmental law,” said Douglas Kendall, president of the Constitutional Accountability Center, a liberal research organization and law firm. Chief Justice Roberts joined the court in 2005, and Justice Samuel A. Alito Jr. in 2006.

Last term’s environmental decisions are consistent with larger trends at the court, which has leaned to the right recently and seems poised to make significant moves in a conservative direction in important areas of the law.

Justice Alito replaced Justice Sandra Day O’Connor, who often voted for environmental interests. Justice O’Connor’s background may have helped shape her thinking: she has written fondly of growing up on the Lazy B ranch in the high desert wilderness in Arizona and New Mexico.

“We experienced nature in an intimate way,” she wrote in a 2005 foreword to her memoir, “Lazy B.” “We learned to respect the environment.”

Justice O’Connor’s departure had a powerful impact and played a part in last term’s 5-to-0 rout, said Amy Sinden, who teaches environmental law at Temple’s law school. “These could all have come out very differently if we still had O’Connor on the court,” she said.

At the same time, the principles announced in some of the court’s environmental rulings, which generally favored presidential power, may aid the Obama administration as it moves away from the previous administration’s policies.

“It’s become a cliché to say the Roberts court is about the expansion of executive power,” Professor Sinden said, “and I think it’s true of these environmental cases as well. The court gave the Bush administration discretion. That certainly leaves the Obama administration with discretion to act as well.”

While the court’s environmental rulings may help the administration as it issues regulations to carry out existing laws, the harder questions will arise as Congress enacts new laws.

“The real test will come when the Obama administration tries to implement new legislation, like the climate change legislation, assuming it passes” the Senate, said Professor Lazarus, who represented the losing side in one of the recent environmental cases.

The climate change law, he said, will “raise a huge number of legal issues when implemented and will face of barrage of legal challenges from industry, some of which will find their way to the high court.”

The Bush administration was largely but not entirely aligned with business interests in the five environmental cases the court decided. That meant it was easy to tell who was losing — the environmentalists — but hard to tell who was winning.

Should the Obama administration take a more adversarial stance toward business, plainer fault lines may emerge.

“You might be able to tell whether the court is pro-business or pro-government,” said Jonathan Z. Cannon, who teaches environmental law at the University of Virginia.

The four members of the court’s conservative wing — Chief Justice Roberts and Justices Alito, Antonin Scalia and Clarence Thomas — and Justice Anthony M. Kennedy, who is often the swing vote, were in the majority in all five decisions. (Justice Kennedy, Professor Lazarus said, has been in the majority in all but one of the more than 50 environmental cases he has heard since joining the court in 1988.)

In years past, Justice Kennedy has been sporadically receptive to arguments made by environmentalists, particularly when they were sensitive to states’ rights and did not call for upending rules on which businesses had come to rely. Not this year.

The five more conservative justices were sometimes joined by Justice Stephen G. Breyer, who is something of a moderate on environmental issues, having written on regulation, risk management and administrative law as a professor before joining the court.

One case, Burlington Northern v. United States, about who may be held liable under the federal Superfund law for toxic spills, was decided 8 to 1, with Justice Ruth Bader Ginsburg in dissent.

Several scholars said that businesses had become more sophisticated in recent years in hiring Supreme Court specialists to tailor their cases to appeal to Justices Kennedy and Breyer.

As surprising as the results in last term’s five cases were, scholars added, what may have been even more surprising was that the court chose to hear some of them at all. In two, the government did not file an appeal, even though the Environmental Protection Agency had been on the losing side in lower courts.

Environmental interests had won in the appeals court in all five of last term’s cases, and the Supreme Court reversed each one. Four cases came from the United States Court of Appeals for the Ninth Circuit, in San Francisco, which has a liberal reputation. The fifth came from the Second Circuit, in New York, and was written by Judge Sonia Sotomayor, now President Obama’s nominee for the Supreme Court.

Should Judge Sotomayor be confirmed by the Senate, she will replace Justice David H. Souter, an avid outdoorsman who loves hiking in New Hampshire and tended to vote in favor of environmental interests.

There is little reason to think Judge Sotomayor’s approach would be very different. Indeed, the court reversed one of her decisions in Entergy Corp. v. Riverkeeper, the case that involved the use of cost-benefit analysis by the environmental agency. Justice Souter was in dissent.

Patrick A. Parenteau, who teaches environmental law at Vermont Law School, said he was disturbed not only by the substance of the court’s recent decisions but also by what they failed to address. None, he said, involved extended discussions of the environmental consequences, whether for the future of a lake in Alaska or the practice of forestry.

“The lesson from this,” Professor Parenteau said, “is to do everything you can to keep environmental cases out of this court.”