A total of around 100 billion species have existed on Earth, which is roughly the same number as the people who have ever lived, and the stars in our galaxy. But each species usually only survived for a few million years before becoming extinct, with or without living descendents to follow it. There are rare, exceptionally long-lived species, such as the Chinese maidenhair tree or ginkgo, which goes back unchanged to fossils 270 million years old, and has no living relatives.
But generally there has been a continual turnover of species, as new ones have arisen in response to new opportunities in the environment, and others have died out because they were unable to cope with change and competition. This is the ‘background’ extinction rate, but there are also events when many extinctions have clustered together in time, called mass extinctions.
Some mass extinctions were quite devastating, with 70% of all species lost in the event of 350 million years ago (mya), and 96% of all marine species and 70% of all land species dying in the one of 251 mya. The mass extinction of 200 mya was less severe, taking 20% of all species, and that of 65 mya killed 50%, but these included almost the entire dinosaur fauna, thus setting the scene for the ‘age of mammals’ (and birds, which are descended from the surviving dinosaurs).
At least a dozen causes of these past mass extinctions have been proposed, including volcanic events, sea-level change, the impact of extraterrestrial bodies, and sudden or sustained global cooling or warming, all with various mechanisms and all implicated in at least one extinction event.
In the modern world, we share our planet with a very large number of other species. No one knows how many, but my own favourite number is 50 million plus or minus 25 million. Sometimes, you’ll come across estimates as low as 10 million, or as high as 100 million. Or more, since you’ll also find discoveries implying that there are 30 million beetle species in tropical forest canopies, or 100 million nematode species in the sea bed alone.
But at this level, the numbers don’t really matter. The thing to remember is that there are a lot of them, and only about two million have been described anatomically and have scientific names, which in most cases is the limit of what we know about them. The other thing to remember is that we’re killing them in vast numbers, either at once, day by day, or by committing them to extinction as their populations and habitats shrivel.
The extreme rate at which species are dying out now will appear in the fossil record of the future as yet another mass extinction. This will be clearly understood, if a successor species exists that’s able to understand at all, as having had a completely new cause: humanity. For the evidence millions of years from now will be unambiguous. There’ll be an extremely thin layer of rock dividing deeper levels full of diverse fossils from shallower levels with hardly any.
The marker layer will contain abundant plastic polymer molecules, radioactive decay products that can only have come from artificial nuclear fusion, and distinctive concentrations of metals. In geological terms it will be called the Anthropocene, the Age of Mankind. Everything afterwards will be the post-Anthropocene, just as the three billion years or so before the Cambrian is now known as the pre-Cambrian.
One reason for this bleak outlook is the ecosystem change that’s now going on, which is simply depriving wild species of their habitats. But few appreciate the true scale of the mass extinction that is now underway. The Earth’s millions of species are not evenly distributed, and about 70% of the terrestrial ones have been found to be concentrated in 34 biodiversity hotspots.
Between them, these once occupied about 15.7% of the planet’s land area. But 86% of this habitat has already been destroyed, mostly since 1950, and the remnants of the hotspots now occupy only 2.3% of the Earth’s land surface. These small and declining patches shelter many species that occur nowhere else: at least 150,000 endemic plant species, almost 12,000 endemic vertebrates, and many millions of invertebrates, mostly unknown to science.
It isn’t possible to slash and burn 86% of the habitats of tens of millions of species without at least half of them going extinct. Not necessarily at once, but committed to extinction they will be, due to the reduction and fragmentation of their populations and habitats, and such factors as the deaths of partner species, such as their pollinators and seed-dispersers. So if the whole dynamic was stopped today, we would still be looking at millions of species continuing to die out, probably at an accelerating pace as the struggle ends for thousands of ecosystems.
This seems set to peak in the period 2000-2025, when half of the world’s species are likely to be lost, at a rate of about a million a year. The continuing growth in demand for farmland, timber and minerals is a major factor in all this, but another is climate change. This is being caused partly by rapid ecosystem change that releases vast clouds of greenhouse gases, but it’s mainly due to the burning of fossil fuels, which does the same but even faster. The consequences may well prove to be the defining feature of the Anthropocene.
Biodiversity is the variety of life, so for many purposes can be thought of as the information contained within living systems. Such systems include the DNA and other forms of coding within individual organisms, lineages and ecosystems. These codes help determine the chemistry and behaviour of organisms and how they fit together into networks of connected organisms (pollinators, seed-dispersers, parasites, hosts, etc.). The vast networks of the natural world – the planetary ecosystem (or biosphere), all the local ecosystems that comprise it, and all the organisms and distinctive species within them – are now being destroyed very rapidly.
Efforts to oppose this are known as nature conservation, and biodiversity management is a key part of that. This is because our technology increasingly allow information to be seen and used as a resource. This is why the Convention on Biological Diversity of 1992 talks about the ownership of genetic resources, access to them, and how the benefits are distributed. Hence, there is an emerging awareness of a biodiversity sector that has distinctive investment needs and attributes, while also being extremely large, complex and interactive with other sectors. It can be defined to include everything to do with:
saving biodiversity (e.g. the design, protective management, financing, use, planning, staffing and inter-sectoral significance of protected areas and protected area systems; the management of genetic resources, species, populations and ecosystems outside protected areas; the suppression of alien invasive species, fires and other factors that pose a threat to wild species populations; and relevant legislation and policies);
studying biodiversity (e.g. all actions to do with research and inventory work involving the collection of information of any kind related to any aspect of genetic resources, species, populations and ecosystems and the organization and use of that information);
teaching about biodiversity (e.g. all actions that use information about biodiversity for an educational purpose whether commercialized or not); and
using biodiversity (e.g. in agriculture, medicine, bioprospecting, ecotourism, natural history film-making and journalism).
These four dimensions of the sector respectively concern the survival of the raw material upon which it is based (and coincidentally vital ecological services as well), the expansion and organization of our knowledge about it, the stimulation of our minds to think creatively about how to use it, and the application of our energies to creating wealth from it.
These four kinds of process cannot sustainably be developed on their own. This because using biodiversity depends on studying it (to gain understanding of what it is and how it might be used), and saving it depends both on teaching about the value of it (to gain public support) and also using it sustainably (to gain revenues to pay for for long-term conservation).