As the drought in California continues threatening plants, animals and insects, there is one species that is thriving – the monarch butterfly. For several decades, the number of monarch butterflies has been on the decline. Recently, scientists have considered adding them to the endangered species list. But with the prolonged drought, we have seen an increase in their numbers and it’s all thanks to milkweed.

Many California homeowners are ripping up their browning lawns and replacing it with drought-tolerant milkweed. Monarch butterflies cannot survive without milkweed, which is where they lay eggs. Once hatched, the caterpillars eat milkweed before spinning into a chrysalis.

“If you plant it, they will come,” Tom Merriman, who has a greenhouse filled with 8,000 milkweed plants of a dozen varieties, told the Associated Press. “We had chrysalises on shovels, we had them on wheelbarrows. They were up in the nursery on palm trees. They were everywhere, under tables. We were releasing 500 caterpillars a week on native milkweed.”

The drought in California has received negative attention – and rightly so – but the return of the monarch butterfly is a small, and beautiful, silver lining.