All hail the Pussy Hat, the charming, knitted-or-crocheted pink cap, designed to raise awareness of women’s rights.

It’s hard to point to anything that has so captured the global imagination and sung the praises of needlecraft at the same time. An exception may be Crochet Coral Reef: CO2CA-CO2LA Ocean, an exhibition by twin sisters which runs through May 6 at the University of California, Santa Cruz (UCSC).

Margaret Wertheim is a science writer. Her sister Christine Wertheim teaches at the California Institute for the Arts. They both grew up in Queensland, Australia, home of the the Great Barrier Reef.

Crochet Coral Reef is a massive collection of individual works of art: corals, anemones, sponges, and other colorful sea-life forms. The artists crocheted the pieces not just from yarn and thread, but also from a cornucopia of flotsam — plastic bags, ties, can flip-tops, videotape, ribbon, and tinsel.

The Crochet Coral Reef project has been exhibited all around the world over the past 10 years, at places like the the Smithsonian National Museum of Natural History in Washington, D.C., the Cooper-Hewitt National Design Museum in New York, and the Hayward Gallery in London.

The materials the artists use to create the work may be soft in feel, but the reef sends out a strong activist message. “My sister and I started the project with the direct intention of bringing attention to the plight of coral reefs, which have been devastated by global warming,” Margaret Wertheim says. “You do get to have a conversation about what’s happening.”

Crochet may not seem like the most obvious medium to make a point about the devastating effects of climate change on reefs. But “hyperbolic crochet,” as discovered by Cornell University mathematician Daina Taimina, is a remarkably effective way to demonstrate mathematics as it appears in nature. Loopy “kelps,” fringed “anemones,” crenelated “sea slugs,” and curlicued “corals” all model algorithms.

A Collective Project

Part of the project’s continuing appeal is the community aspect. Wherever the Crochet Coral Reef travels, exhibition organizers wrangle members of the local community to crochet an auxiliary reef of their own. This includes Santa Cruz, where the exhibition is a co-production of the Mary Porter Sesnon Art Gallery and UCSC’s Institute of the Arts and Sciences.

The gallery hosts a selection of what’s been created before in each city. The Institute is coordinating crocheting circles on campus, in downtown Santa Cruz and at the Seymour Marine Discovery Center, where UC Santa Cruz’s “satellite reef” will be presented in May.

Almost 300 people have gotten involved so far, including the Santa Cruz Knitting Guild, The Fábrica, and Rachel Nelson, curator and program manager of the Institute. There are monthly workshops at the Seymour Marine Discovery Center, and weekly workshops on campus. “I quickly had to learn, so I could help teach people how to crochet,” Nelson says, adding that community members have mostly relieved her of her teaching duties. “This is the first project I’ve been on that has had this level of community engagement.”

Mimicking Mother Nature

Besides fostering community and conversation, the “many hands” approach is meant to make a statement about Mother Nature. “It takes hundreds, sometimes thousands of people to build these community reefs,” Margaret Wertheim says. “That’s exactly how corals work. Each polyp alone has no power on its own. But collectively, they can build the great barrier reef. When we act together, we can really do extraordinary things.”

Margaret Wertheim says the Mary Porter Sesnon Gallery is much smaller than the other spaces the Wertheims have worked with in the past. This forced the sisters to get creative. “How can we make something fabulous for this particular space?” Marget Wertheim says.

One idea the Wertheim sisters came up with was to use the aerial space in the gallery. Suspended from the ceiling, “The Midden” is a fishing net filled with four years’ worth of domestic trash. “Every bottle, every piece of wrapping that we used in our daily lives,” Margaret Wertheim says. The work is meant to be a reflection of the Great Pacific Garbage Patch, seen from a “fish’s eye view.”  

As global warming accelerates, “It’s now very, very clear that we are in deep trouble,” Margaret Wertheim says. “What’s needed is to keep on pushing, whether gently or aggressively, the notion that climate change is caused by humans. I think our project has done it, in a way that’s gentle and accessible to people.”

‘Crochet Coral Reef: CO2CA-CO2LA Ocean’ runs through Saturday, May 6, 2017 at the Mary Porter Sesnon Gallery on the UC Santa Cruz campus. More info here.

To join one or more of the crocheting workshops, check out the schedule here.