Cabo Dorado -- the latest iteration of a massive coastal tourism and real-estate project planned for Mexico's Baja California peninsula -- is once again worrying local activists.

Over the last several years, one version or another of a mega-resort neighboring Mexico's Cabo Pulmo National Park has been put forward by various groups of investors. The last attempt, dubbed Cabo Cortez, was squashed by Mexican President Felipe Calderon in 2012.

But now the proposal is back, this time backed by Chinese investors, and environmentalist fear construction could begin as soon as permits are granted.

An alliance of environmental activists say the $3.6 billion project would spell catastrophe for the region's biodiversity.

"The Cabo Dorado project must be avoided at all costs due to the large amount of regional impacts that would jeopardize the environmental viability and people's wellbeing in that region in the short, medium and long term," groups such as Friends for the Conservation of Cabo Pulmo, the Mexican Center for Environmental Rights, Wildcoast and Greenpeace wrote recently in a letter opposing the development plans.

In another op-ed, activists characterized their defense of the Baja California peninsula as a last stand.

"Too many times along the coasts of Mexico we have witnessed the wholesale destruction of areas of great biological and cultural importance," wrote co-authors Sula Vanderplank, a biologist at the Botanical Research Institute of Texas, and Benjamin Wilder, a researcher at University of California, Riverside.

"On the headlands and mangrove estuaries of La Paz, Loreto, and other Baja California coastal cites," they added, "biologically important land has been razed for ambitious hotels and apartments."

Wilder helped produce a report outlining the ecological value of the lands surrounding the area of proposed development.

"Until recently, the biological value of the lands adjacent to the coral reef of Cabo Pulmo had remained a mystery," said Wilder. "We now know that these desert lands mirror the tropical waters in importance. This desert-sea ecosystem is a regional biodiversity hotspot."

Meanwhile, investors argue their 3,770 hectare project -- featuring 22,500 hotel rooms -- is scaled back and respectful of the environment compared to similar resorts in the region.

Cabo Dorado's official website claims its plans are "unique in the sense that the real estate density has been considerably decreased and the ecological reserve allotted to the conservation of the environment has been increased significantly."