More than 50 of Canada's leading scholars and scientists are urging Parliament to make major changes to a signature bill from Prime Minister Mark Carney's government in an effort to avoid irreversible environmental harm for the sake of fast-tracking projects.

In an open letter sent Thursday, 56 fellows of the Royal Society of Canada propose six significant amendments to Bill C-39, the Building Canada Strong Act, which is being reviewed by special committees in the House of Commons and Senate for swift passage.

The goal of the 243-page bill is to speed up decisions on projects to give greater certainty to proponents and investors by establishing a one-year review deadline and regions of national interest where certain types of projects can be pre-approved.

The fellows say they support the federal government's decision to create conditions for investment, jobs and economic growth, but they say the bill as written goes too far to endanger nature, wildlife and human health.

"Bill C-39 countermands the environmental protections currently in place in Canadian law, laws written to avoid irreparable harms," the fellows wrote. "We call upon the House and Senate to uphold these laws and to consider our recommendations for the benefit of nature, Canadians and the rest of the world." The Royal Society of Canada is considered the country's senior national bilingual academy. It recognizes academic, artistic and scientific excellence and its members often advise government. There are more than 2,000 Royal Society of Canada fellows, according to the academy's website.

Bill C-39 proposes to amend more than a dozen pieces of federal legislation, including laws that protect species at risk, fisheries and water quality.

It also intends to eliminate a five-year sunset clause that limited the government's extraordinary powers under initial Building Canada Act, Bill C-5, to exempt certain projects deemed in the national interest from a wide set of environmental regulations and acts of Parliament. The fellows are asking parliamentarians to keep the sunset clause in place.

Carney government accused of stalling on Indian Act reform U.S. Embassy says Canada brushing off 'potential interference' in midterms They're also looking for regions of national interest to be fully defined, an acknowledgement that additional time may be required to evaluate projects and thorough reviews before shovels hit the ground, among other amendments.

"This is not a build Canada while protecting our environment act," said Sarah Otto, a professor in the department of zoology at the University of British Columbia, who signed the letter. "It is a build Canada strong while damaging the environment [act]."

Potential long-term consequences The letter is the latest step by scientists and environmentalists to raise alarms about Bill C-39, as the governing Liberals use their majority to push through the controversial proposed legislation without the usual time allotted for parliamentary debate and review.

"Some of the changes that can be happening are going to affect ecosystems forever," John Smol, a Queen's University biology professor who signed the letter, told CBC News.

"We really have to take into consideration what are the long-term consequences and who's paying for this? It's not going to be the industry, it's going to be our children and grandchildren." Federal ministers defended Bill C-39 on Monday at the special legislative committee in the House of Commons.

"Clearer timelines do not predetermine outcomes, and responsible developments and robust oversight can and should exist together," said Dominic LeBlanc, minister responsible for Canada-U.S. trade, intergovernmental affairs and one Canadian economy.

All opposition parties say they're planning to suggest amendments to Bill C-39 to address environmental concerns and another contentious proposal to change the Labour Code. Unions warn the bill will limit the right to strike, but the government says the proposed legislation will protect it.