Matt Nolan, who runs a mapping business in Alaska using aerial photography, was flying a small plane to the Arctic National Wildlife Refuge in the northeastern part of the state last month when he noticed a pattern on the tundra.

Nolan, a geophysicist, saw a grid of tracks left by heavy vehicles involved in recent seismic testing for oil and gas exploration in an area called Point Thomson. The tracks, several hundred yards apart, were as regular as a checkerboard and ran across the landscape just outside the refuge.

A similar dense grid may soon cover some of the refuge itself, perhaps as early as December, if seismic testing starts under a plan to sell leases for oil and gas exploration that was approved by Congress last year and that is strongly opposed by environmental and conservation groups. The northern part of the refuge, 1.5 million acres of the Arctic coastal plain known as the 1002 Area, is thought to overlie billions of barrels of oil and gas.

Disturbances like the tracks Nolan saw could remain for decades or longer like a tattoo on the refuge, a vast tableau of mosses, sedges and shrubs atop permafrost that is considered one of the most pristine landscapes in North America. There are still signs, for example, of a much less dense pattern of tracks from the only other time testing was allowed there, in the mid-1980s, and of the only drilling pad, which was built at the same time.

Any new tracks could also potentially alter how surface water flows in the tundra, draining lakes or accelerating the thawing of permafrost in some areas.

Nolan spent most of July flying across the 1002 Area making an elevation map that will serve as a baseline for any changes to come. When he saw the tracks outside the refuge he decided to map those as well. He found that they were up to half a foot deep.

Nolan, a former research professor at the University of Alaska in Fairbanks, said he was not taking sides in the fight over drilling in the refuge, “but I want to make sure that whatever happens out here happens in the most responsible way.”

“Leaving grid marks all over — that to me is unacceptable,” he said.

Environmental and conservation groups, which have fought to preserve the 19-million-acre refuge for decades, say that seismic testing, not to mention eventual drilling and production of oil and gas, could irreversibly alter the 1002 Area and potentially affect the habitat and behavior of caribou, polar bears and other animals there.

“There’s not a lot in here that you can look at and feel good about,” said Kristen Miller, conservation director of the Alaska Wilderness League, referring to a plan for testing in the 1002 Area put forth this year by a seismic services company, SAExploration, and two Alaska Native corporations.

That plan proposes that testing begin this winter, when ice and snow provide some protection to the tundra, and resume, if necessary, the following winter. In addition to special trucks that vibrate the ground, the effort would include movable fuel tanks as well as housing and other facilities for two crews of 160 workers each. In the plan, the company said it and its partners were “dedicated to minimizing the effect of our operations on the environment.”

By producing three-dimensional images of the subsurface, the testing would help oil companies determine whether there are enough reserves to make it worth buying leases to drill in the area.

The plan drew criticism from the U.S. Fish and Wildlife Service when it was first put forth in May. But another agency of the Interior Department, the Bureau of Land Management, will review the plan and decide whether to allow testing. Lesli Ellis-Wouters, a bureau spokeswoman, said that SAExploration had been asked to provide more information.

The approval process includes conducting an environmental assessment, a less-thorough appraisal than an environmental-impact statement, or EIS, although the bureau can require an EIS later if the initial review finds the work could result in significant impacts.

Ellis-Wouters said there would be a 30-day public comment period when the assessment is finished.

Sue Natali, an ecologist at Woods Hole Research Center in Massachusetts who studies Arctic tundra and permafrost, said that depressions, even shallow ones, can have cascading effects. “The ground sinks, so it gets wetter,” she said. Since water carries and conducts heat, the land thaws more and then sinks more. “The impact can last for a very long time,” she said.

Ellis-Wouters, the bureau spokeswoman, said that hydrological and visual impacts, as well as effects on vegetation, would be considered in the review. “The visual impacts are only detected from the air,” she added.

She said the bureau expected that more advanced 3-D testing technology would result in less surface impact than the work done in the 1980s.

Nolan acknowledged there was little time to pressure the Bureau of Land Management or exploration companies to change their approach. Still, he said, the existence of his new map may have an effect.

“I hope the oil and gas people understand that someone’s watching,” he said. “When you know someone is watching you get on better behavior.”