Conservationist sheep come to the rescue in Pompeii: In a bid to protect the unexcavated ruins of Pompeii from being overrun with plant growth, archeologists have deployed a flock of 150 sheep to graze around the historical site, Reuters reports.

Low cost, low emission approach: “We try to have a sustainable approach to the whole environment to avoid using [harmful] substances,” director of the Pompeii Archaeological Park Gabriel Zuchtriegel said, adding that the initiative also saves money while preserving the Roman city’s landscape. Only two thirds of the 163 acre city — buried under meters of pumice and ash from a volcanic eruption 2k years ago — have been uncovered since excavations began 250 years ago.

But not all grazing is zero-risk: Overgrazing can destroy native vegetation, damage soil, disrupt natural processes and ecosystems, and contaminate surrounding water sources, the Center for Biological Diversity explains.