There are 22,413 species deemed at risk of extinction by the International Union for Conservation of Nature (IUCN). If some ambitious person tried to read out their names — without any breaks for food or water — it would take at least half a day. But that would be just the start. The IUCN has assessed the status of only 76,199 of the 1.7 million species of animals, plants, fungi and protists on Earth that have been described by scientists. And some suggest that at least five times more species still wait to be discovered. Many of these are also threatened, and it would take months to read out all of their names. (Except that they do not, of course, have names.)

There remain vast gaps in knowledge about the planet’s biodiversity — and the precarious state of life. Every day, animals and plants go extinct. Nobody knows exactly how many, but estimates range from 500 to 36,000 extinctions per year. A News Feature on page 158 draws together some of the best studies of biodiversity and tries to make such vast numbers fathomable.

Before human populations swelled to the point at which we could denude whole forests and wipe out entire animal populations, extinction rates were at least ten times lower. And the future does not look any brighter. Climate change and the spread of invasive species (often facilitated by humans) will drive extinction rates only higher.

The pace of extinction is leading towards a crisis. If all currently threatened species were to go extinct in a few centuries and that rate continued, the die-offs would soon reach the level of a mass extinction — the kind of biological catastrophe that ended the reign of the dinosaurs and that has happened only five times in Earth’s history. The sixth mass extinction could come in a couple of centuries or a few millennia, but it lies somewhere in the future if nations keep to their present course.

There are some hopeful signs. Countries are rapidly expanding the areas they shield from destructive human activities. The United Nations Environment Programme (UNEP) announced last month that countries have set aside 6.1 million square kilometres of ocean and land habitat since 2010, which increases the total protected areas to 15.4% of Earth’s land and 3.4% of its oceans. According to UNEP, countries are on track to meet a 2020 goal established under the Convention on Biological Diversity to protect 17% of land areas, although reaching the 10% target for coastal and marine regions will require further efforts. The total areas set aside now equal the size of Africa.

But these efforts are not enough. Many protected zones are ‘paper parks’, where hunting, fishing and habitat destruction continue apace because of lax enforcement. And most parks established so far do not protect the most crucial areas — the ones full of threatened species and habitats. Nations are also investing much less on protection than they were 15 years ago, after adjustments are made for inflation.

In the face of this uncertainty about biodiversity, what should the world do? UNEP estimates that it would take US$76 billion each year to establish and manage a set of expanded parks that protect important habitats for all wildlife groups. That figure is just as unfathomable as the number of species on the planet. But consider that a blockbuster video game can sell $500 million in copies in a single day. According to UNEP, the economic benefits of protected areas far outweigh their costs, which could be met through a mixture of conventional sources and innovative funding mechanisms, such as green taxes and payments for the services that ecosystems provide.

As part of this protection effort, nations also need to devote more resources to taking stock of life. The IUCN has set a 2020 goal of assessing 160,000 species, roughly double the current number, which it calculates would cost $60 million and cover a good representation of most major taxonomic groups and ecosystems. The job of counting and evaluating is not the most exciting science. But it is one of the most fundamental and important tasks that humans can do — to take a measure of life and protect what remains before it disappears.