Here today, gone tomorrow.

We are destroying the life-support systems of Earth rapidly, making our future uncertain. Ecosystems—the complex sets of organisms that form the globe's living landscape—regulate the atmosphere, water, and soils. They supply humanity its food, most medicines, and many other essential products, and they fill our lives with beauty. But they are falling apart as, one by one, their constituent species are lost. To save what we can and provide our children and grandchildren with a sustainable future, studies must be conducted not only in nature but also, to an increasing extent, on the billions of specimens preserved in the world's natural history collections. For many species barely hanging on in their endangered habitats, these samples will one day be all that we have. Last week's United Nations Summit on Biodiversity discussed earlier reports that perhaps 1 million of the estimated 8.5 million species of plants, animals, and other organisms are in imminent danger of extinction. Probably as many as half of the populations of organisms that existed half a century ago are already gone. Over the past quarter century, about a quarter of all tropical forests have been lost. Because we have identified no more than a tenth of the estimated tens of thousands of species in those habitats, most that were lost may forever remain unknown. Unless we control the underlying causes, including overdevelopment and climate change, we are in danger of losing 80% or more of the world's species, the proportion lost 66 million years ago when the dinosaurs became extinct and many of the plants and animals known today began their ascent. We have clearly entered the world's sixth major extinction event. While we work to forestall this destruction, we must treat the specimens in our collections with ever more care. They are no longer simply samples of wild populations from which more will always be available. As many as half of the specimens likely represent populations that no longer exist, and an increasing number of species as well. What is in our collections will often turn out to be all that remains of organisms that once thrived. Faced with this grave future, we must find ways to preserve these specimens as well as we can for as long as we can. They are vulnerable to degradation and loss from pests, humidity, fire, and the simple ravages of time. While renewing efforts to protect them, we need to make them more accessible through digitization, including imaging and DNA barcoding (at least a minimal DNA sequence of the representative specimens). We also need to continue targeted sampling, focused on key taxa and habitats. Some groups of great ecological and environmental importance are dying off too rapidly to ever be completely understood. We have named 25,000 species of nematodes, 64,000 species of mites, and 100,000 species of fungi. Yet each of these groups is estimated to consist of a million or more species, with the number of fungi likely to be 2.2 to 2.6 million. We must sample them and understand them as well as we can before many of their species disappear forever. To do all of this, we need many more specialists in all regions of the world who are trained in advanced methods for collecting and preserving specimens, and in the exciting new field of “museomics”—determining DNA sequences from old preserved specimens. The standards for the best preservation and training established by the International Society for Biological and Environmental Repositories may help point the way. Many of the world's biological collections are in institutions that depend in part on attendance for their support. In this time of coronavirus disease 2019 (COVID-19), many of them will fail financially or be unable to continue maintaining their own collections. These and other potentially “orphan” collections have immense value and should be monitored and incorporated as needed into permanent homes. This is likely to be our last chance to know many of Earth's species. We must make the most of it.