Non-Toxic Fern Covers Surface of Lake Anza in Berkeley
BERKELEY (KPIX) -- A lake in Berkeley's Tilden Park has seen an amazing transformation thanks to a tiny plant that is thriving due to the drought.
What looks like a flat meadow in Tilden Park isn't a meadow at all. It's actually Lake Anza. Hiker Bruce Stangeland was surprised by what it looked like on Monday.
"It's not a lake anymore. It looks like a lawn," he said with a laugh.
The two-acre lake has seen an explosion of a non-toxic plant called the Azolla fern. Now the top of the lake looks more like a carpet, with a perfectly still, greenish-brown covering almost every inch of its surface.
Azolla is not new to the area, with the floating covering made up of clumps of tiny ferns. The plants can be beneficial, used in Southeast Asian countries for everything from fertilizer to feed for animals, including fish.
That's why Stangeland took some home for his fishpond a long time ago.
"I said, if the fish are going to eat them, I don't have to feed them anymore and I've had...some of them are probably 20 years old," he said. "It is pretty amazing stuff, yeah. And it keeps the water clean, so there's no algae in my pond."
The Regional Park District says it's also crowding out the toxic algae that sometimes plagues the lake and is keeping the water cooler to help the local trout. As tp why the fern has sprung up in such volume now, park biologists think Lake Anza has been stilled by lack of rainfall, low water flow and an absence of swimmers when the beach was closed during the pandemic. That has allowed the ferns to flourish.
It's giving visitors a view of one of nature's weirder spectacles.
"I came up here through the trail and I was like, 'Wow, look at this field!' And then I looked back there and I could see the water. And I was like, 'Wait, this is a lake!'" said visitor Jose Cervantes.
"Honestly, it's very welcoming," said his friend, Thomas Lee Tipton. "As long as it's nothing bad, it's cool to look at. It's definitely worth it. I'm definitely glad that we went out to find something nice and we found this."
And while it may seem like something you could walk across, a five-year-old visitor named Adi wasn't letting the ferns fool her.
"It looks like you could just -- BLOOP! -- sink in when you step on it!" she said.
Swimming has been prohibited since 2019 and park officials said they planned to close it for another year anyway, due to maintenance projects. So they are leaving the lake as it is.
That will give biologists a chance to study the plant's growth and its effects on the ecosystem. No one is sure how long it will last, but they're willing to let nature take its course for now.