From afar, a casual viewer could mistake the coral reefs on display at Washington’s Natural History Museum for the real thing, but in fact, it’s colourful crochet artwork with an environmental message.

The exhibit is the work of some 800 women, and a few men too, who hope to draw attention to the plight of the world’s coral reefs, which face stress, degradation and outright extinction because of damaging human activity.

Participants ranging in age from three to 101-years old responded to a call for project volunteers by organisers Margaret and Christine Wertheim, Australian activists with the Institute for Figuring.

The results are captivating pieces of work – barriers of coral that stand three metres tall, with multicoloured strands of wool that mimic the curves and curls of coral, anemones and starfish.

Fluffy stubs with threads in red and green sit next to pink and purple structures with curling edges that seem to undulate as they would in the water deep beneath the ocean’s surface.

The exhibit is entitled Hyperbolic Crochet Coral Reef, a reference to the hyperbolic geometry of coral, which has so far proven impossible to reproduce physically except through the medium of crochet, organisers say.

“We like to surprise our visitors. You don’t expect to see crochet... in a Natural History museum,” said Barbara Stauffer, chief of temporary exhibits at the Washington institution.

Coral reefs worldwide face multiple threats from human activity, including global warming, which raises the ocean temperatures to dangerous levels, and acidification, which can bleach and kill coral.

Overfishing and pollution also threaten the survival of the delicate ecosystems, which could disappear altogether over the next four decades, experts warn.

“The reefs that I studied 35 years ago have largely vanished and most reefs may well be gone by the end of the century of sooner, if nothing is done to protect them,” said Nancy Knowlton, a professor of marine biology at the Smithsonian Institution.

The exhibition, which runs till April 24 carries a serious and sad message about the state of the world’s coral reefs and the negative effects of human activity.

But Margaret Wertheim said the creative and unusual pieces also offer a positive message about what can be produced by people working in coordination and collaboration towards a common goal.

“The reef project is a giant explosion of feminine energy, a testimony to what women can achieve when they work together.”