EDMONTON - Scientists are joining the battle over a plan to phase out the use of off-highway vehicles in two ecologically sensitive parks in southwestern Alberta.

Last January, the province announced a draft plan for the Castle Wildland Provincial Park and Castle Provincial Park to preserve just over 1,000 square kilometres of mountains and foothills.

Since then, groups that represent people who drive ATVs, trucks and jeeps have protested against the plan that would ban them from these areas within five years.

On Tuesday, 57 scientists sent an open letter to Alberta Environment Minister Shannon Phillips urging the province not to back down.

"The decision to remove off-highway vehicle use from the Castle and restore damaged areas will contribute to the conservation of native vegetation, fisheries, wildlife, soil and community water," reads the letter.

"The science is clear that motorized use, even under controlled circumstances, has a negative impact on these natural features."

The letter is signed by scientists at the universities of Alberta, Calgary, Lethbridge and other schools in Canada and the United States.

For years the Castle region has been mined, logged and drilled for oil and natural gas.

It is home to more than 200 species of endangered plants and animals and is considered a key link for grizzly bears that move north and south.

David Schindler, an award-winning water expert at the University of Alberta, said he supports the ban even though he owns ATVs.

"I have had three hip replacements on two hips and own ATVs, yet I still support the removal of this land use as I understand the impact of even a small amount of noise and disturbance has on water and on sensitive wildlife," he wrote.

The government has received the letter.

Phillips said the plan for the Castle area is guided by science-based decision making and reflects the increase in the Alberta's population in recent years.

"We're taking steps to ensure the Eastern Slopes are better managed to protect livelihoods, recreation and conservation," she said in an email.

"We will invest in infrastructure so off-highway vehicle users can still enjoy less sensitive areas. And we will work to protect biodiversity, drinking water and the natural beauty of the Castle area for future generations."

When the Alberta government announced its draft management plan for the parks on Jan. 20, it gave people 60 days to respond, including through an online survey. The deadline has been extended to April 19.

Since then off-highway vehicle groups have held protests, including at the Alberta legislature and in the town of Blairmore in the Crowsnest Pass.

These groups estimate that up to 1,000 off-highway riders and random campers use the Castle area on a summer long weekend.

In March, the government revised the plan. The changes include not putting it into effect in the upcoming season and to allow hunters to use trail networks to recover game.

A group of riders known as the Crowsnest Pass Quad Squad said they continue to oppose the proposed ban.

"We still feel that we can protect the environment by maintaining proper trails," said Gary Clark, the group's president. "We are frustrated and angry."

Clark noted that more than $2 million has already been spent in the Castle wilderness over the years to build bridges and move trails away from streams.