“We need the tonic of wildness,” writes Henry David Thoreau in his 1854 classic Walden; or, Life in the Wood. “We can never get enough of nature.”

Had he lived in our time, Thoreau would’ve been thrilled to know that the Biodiversity Heritage Library (BHL), the world’s largest open-access digital archive dedicated to the natural world, is now offering more than 150,000 high-resolution illustrations for copyright-free download.

These public domain images belong to an archive of more than 55 million pages of literature about earth’s species of flora and fauna. They include animal sketches, historical diagrams, botanical studies, and scientific research collected from hundreds of thousands of journals and libraries across the world. Some of the illustrations date back to the 15th century.

According to BHL, sharing these documents with the public is instrumental in combating the climate crisis. “To document Earth’s species and understand the complexities of swiftly-changing ecosystems in the midst of a major extinction crisis and widespread climate change, researchers need something that no single library can provide — access to the world’s collective knowledge about biodiversity,” the library says on its website.

It continues, “While natural history books and archives contain information that is critical to studying biodiversity, much of this material is available in only a handful of libraries globally. Scientists have long considered this lack of access to biodiversity literature as a major impediment to the efficiency of scientific research.”

The collections are a feast to the eye. Among them, you’ll find a digitized copy of Joseph Wolf’s 19th-century book Zoological Sketches, containing about 100 lithographs depicting wild animals in London’s Regent’s Park. You’ll also find watercolors depicting flowers indigenous to the Hawaiian islands, and an 1833 DIY Taxidermist’s Manual.

To enhance research, the library also offers search features to find species by taxonomy and an option to follow online conversations about books and articles in the archive. As it continues to add collections to the public domain, the library is currently working on a project to promote awareness of the field notes available from the Smithsonian Institution Archives, the Smithsonian Libraries, and the National Museum of Natural History. Launched in 2010, the project’s goal is to catalog 5,000 field books and provide easy access to them.

Selected images from the public domain images are available on the library’s Flickr and Instagram pages.