Originally published in May 2020; updated in November 2024.
The Earth is undergoing a mass extinction that could see up to a million species disappear in the coming decades – thanks in large part to humans.
The numbers are staggering: the population sizes of vertebrate species, which include mammals, reptiles, birds and fish, dropped by around half between 1970 and 2010. A quarter of mammals, 40 percent of amphibians and 30 percent of sharks and rays are currently endangered.
During the 20th century, extinction rates were about 100 times higher than they would have been without humans significantly altering most of the planet’s surface.
What does this loss of biodiversity mean for the future of the planet and its inhabitants – and what can we do about it? Here’s what you should know.
Coined by biologists in the 1980s as a contraction of biological diversity, the term usually refers to the variety of life on Earth as a whole. The Convention on Biological Diversity (CBD) breaks it down as follows:
“Biological diversity” means the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part.
But the CBD makes it clear that measuring biodiversity is no simple feat:
This includes diversity within species, between species and of ecosystems.
Let’s start with biodiversity between species, or species diversity. Arguably the simplest measure is ‘species richness’ – a count of how many species live in a community.
But species richness does not consider the relative abundance of each species, or its importance to an ecosystem or landscape, or its value to people. As such, biologists have invented diversity indices, such as the Simpson index and the Shannon index, to take these factors into account.
When we talk about biodiversity loss, we often measure this in terms of species diversity, which is crucial to maintaining the balance of ecosystems and nutritional value of food, as well as protecting ecosystems and landscapes against the climate crisis and other risks like weeds and pests.
Yet genetic diversity – the characteristics of a species’ genetic makeup – is equally important as it provides resilience against change and stressors at the individual level.
Consider the following analogy: in investing, a diversified portfolio minimizes risk and usually provides the most reliable returns. Likewise, genetic diversity protects a species from being wiped out by an external shock like a natural disaster or disease outbreak.
At the largest scale is the concept of ecosystem diversity, which measures how many different ecosystems exist within a geographical area or wider landscape. The more ecosystems exist within a landscape, the more resilient that landscape is, and the more services it has to offer its inhabitants.
Some examples of important ecosystems are wetlands, which contain over 40 percent of the value of the world’s ecosystems; peatlands, which store a third of the planet’s soil carbon; and lesser-known tropical forests such as monsoon and karst forests, which are among our best natural defenses against the climate crisis.
You might have also heard of ‘biodiversity hotspots.’ These are landscapes with exceptionally high concentrations of biodiversity. Nearly half of all bird, mammal, reptile and amphibian species are only found in areas that make up just 2.4 percent of the Earth’s surface area.
Healthy and functional ecosystems play a crucial role in sustaining human livelihoods through providing necessities and benefits such as food, water, energy sources and carbon sequestration, known as ‘ecosystem services.’
One study estimates that each year, the goods and services provided by the planet’s ecosystems contribute over USD 100 trillion to the global economy – more than double the world’s gross domestic product (GDP).
But there’s much debate over how to factor in non-monetary values, such as natural beauty, regulating functions and providing homes for humans and animals.
Biodiversity underpins all of these ecosystem services. Genetic diversity supports agriculture by building resilience and protecting against environmental stresses such as pests, crop diseases and natural disasters. This provides a source of income and safeguards the food security of much of the world’s poor.
Biodiversity also plays a role in some ‘nature-based solutions’ to the climate crisis and problems caused by changes in the environment. These solutions could provide up to a third of the carbon emissions reductions needed to meet the Paris Agreement goals.
But not every nature-based solution is equally beneficial to biodiversity. Tree planting, for instance, can come in the form of monocultures (planting just a single species in a landscape) or agroforestry, which mixes crops and trees in a single landscape to enable them to support each other.
And let’s not forget: the planet’s ecosystems also hold considerable intrinsic value to humans, whether it’s for their recreational opportunities, their cultural importance to Indigenous communities, or their contributions to physical and mental health. Without biodiversity, these values will be lost.
In a seminal report published in 2019, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) identified five direct drivers of biodiversity loss: changes in land and sea use, overexploitation, the climate crisis, pollution and invasive species.
It says these five drivers are in turn driven by increasing demand for natural resources, as well as governance structures that prioritize economic growth over conservation and restoration.
The most widespread form of land use change has been the expansion of agriculture: according to the IPBES report, over a third of the Earth’s land surface is now used for cropping or livestock, mainly at the expense of forests, wetlands and grasslands.
The tropics, which are home to the highest levels of biodiversity on Earth, are now seeing their ecosystems replaced by cattle ranching in Latin America and plantations in Southeast Asia.
Other key land use changes include logging, mining and urbanization. Coastal and marine ecosystems have also been significantly affected by activities such as offshore aquaculture, bottom trawling, coastal development and deep sea mining.
The IPBES report suggests that fishing has had a larger impact on marine ecosystems than any other human activity: a third of marine fish stocks are currently overfished, and 60 percent are being fished to their sustainable limits. Poaching and hunting, too, are driving many mammals to the brink of extinction.
Humans have caused the planet to warm by around 1.34 to 1.41 degrees Celsius since pre-industrial times – and biodiversity is already bearing the brunt of that warming. The climate crisis is reducing the distribution of many species (the geographical area in which they can survive), including almost half of all endangered mammals.
Changes in the ecological balance can also result in species that can beneficial turning into pests and plagues once their natural enemies are reduced or disappear: think locusts, mosquitos and algae.
Many plants and animals are also experiencing disruptions to their phenology, which refers to seasonal life cycle events such as flowering, migration and hibernation.
Mining, agriculture, industry and other pervasive changes in human land use are contributing to air, water and soil pollution. The IPBES report notes that coastal waters contain the highest levels of metals and organic pollutants, such as industrial discharge and fertilizers.
Similarly, marine plastic pollution has increased tenfold since 1980, primarily affecting marine turtles, seabirds and marine mammals, as well as humans indirectly through the food chain.
An invasive species is a species that has been introduced to a new location and starts to disrupt its new habitat. These species can threaten native biodiversity by outcompeting them for resources, and they’re spreading ever more quickly with the growth of global travel and trade.
A recent study found that one-sixth of the Earth’s land surface is highly vulnerable to invasion, including many biodiversity hotspots.
Humanity’s ecological footprint is about 70 percent larger than the planet can sustain – and in the world’s richest countries, that figure is as much as four or five times larger.
Given these huge inequalities in both living standards and ecological impact, residents of industrialized nations can – and should – do their part to preserve biodiversity by helping contribute to more sustainable global systems.
At the individual level, you can help restore nature by creating space for biodiversity in your backyard or starting your own tree nursery. Your lifestyle choices can also make a difference: try reducing air travel, buying organic, eating less red meat and avoiding fast fashion.
Indigenous and local communities are deep and rich sources of traditional knowledge of how best to care for increasingly fragile landscapes. Technology can be a crucial tool, too.
But it’s important to recognize that the biodiversity crisis has systemic roots, and much more needs to be done at the policy level to tackle it.
And with biodiversity worth more in monetary terms than the entire global economy, there’s a growing case to invest in restoring the planet.
Governments have had a patchy record on biodiversity: none of the Aichi Biodiversity Targets set in 2010 had been achieved by 2020, and the crucial 2020 UN Biodiversity Conference (COP15) was postponed for over two years due to the COVID-19 pandemic.
Then came a breakthrough, as negotiators finally agreed on a new set of global biodiversity goals for 2030, known as the Kunming–Montreal Global Biodiversity Framework (GBF).
These included protecting 30 percent of the Earth’s lands and seas by 2030, as well as restoring 30 percent of all degraded terrestrial and aquatic ecosystems.
And for the first time ever, the GBF also formally recognized the vital role of Indigenous Peoples and local communities, as well as the importance of gender equality, in achieving these goals.
But other goals were watered down as countries squabbled over the fine print, and the GBF left a crucial question unaddressed: who will pay for the protection of our planet’s biodiversity?
That question has remained unanswered following the 2024 UN Biodiversity Conference (COP16). Delegates will reconvene to discuss it further, with the exact date and location to be determined.
Negotiators did, however, agree to create a subsidiary body to protect the sustainable use of biodiversity by Indigenous Peoples and local communities, which also recognizes Afro-descendant peoples.
They also agreed to create the Cali Fund, which will be a global mechanism to protect the use of genetic data and prevent biopiracy. It will aim to ensure that benefits from digital sequence information (DSI) are shared with local communities and not simply pocketed by private companies.
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