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What is biodiversity and why does its loss matter?

Biodiversity is the name we give to the variety of all life on Earth. Bacteria to baboons, plants to people - the range of life on our planet is incredible.

All living things exist within their own communities, or ecosystems - oceans, forests, deserts, ice caps and even cities. All this put together is biodiversity: the volume of life on Earth as well as how different species interact with each other and with the physical world around them.

The word biodiversity is a contraction of 'biological diversity'. The concept is broad and complex, but that complexity is what makes Earth a perfect place for humans to live.

Why do we need biodiversity?

Humans rely on biodiversity to survive. We are intertwined in a big natural system, and each element supports and enables all of us to thrive.

It is easy to see why humans need nature: we need fresh water, clean air, and plants and animals for food. But what we need specifically is biodiversity. Nature around us isn't enough - we need a natural world that is complex, resilient, thriving and full of variety.

Nature needs to be able to cope with change. Different animals and plants in a habitat help to make that place stable and sustainable. Small changes will have fewer effects, allowing it to keep providing us with what we need. 

A collection of colourful butterflies and moths

Every one of these moths and butterflies from the Museum collection is different. They are an example of biodiversity, which means the diversity of life on Earth.

Ecosystem services

The benefits biodiversity brings are called ecosystem services. Biodiversity keeps us all alive, but it also helps to make our lives healthy and safe.

Ecosystem services include forests that diminish floods, coastlines that protect us from changing sea levels, wetlands that regulate pollution and parks that ease our anxiety.

Biodiversity and species richness

When we talk about biodiversity, we often talk about species richness as well. Species richness is the number of different species in an area, a way of measuring biodiversity.

Studying species richness helps us to understand the differences between places and areas.

For example, the Amazon rainforest is very species rich as it is home to at least 116,000 species, including more than 14,000 flowering plants and over 5,500 vertebrate species. In contrast, the Sahara Desert is far less rich, possibly with as few as 500 plants and 300 vertebrate species. 

About 1.7 million species have been described by scientists, and most of them are insects. But it is thought that there are millions more sharing our planet with us.

A collection of deep sea fishes in jars

The ocean is home to a huge variety of life, such as this collection of deep sea fishes. Its thought that the majority of deep sea life is yet to be discovered

Endangered species and mass extinction

Overall biodiversity loss can speed up extinction. More and more animals and plants are facing an uncertain future.

The International Union for Conservation of Nature (IUCN) is the global authority on the status of the natural world. It keeps a Red List of endangered species, an important indicator of the health of the world's biodiversity.

Currently, more than 41,000 species are listed as threatened with extinction, which is 28% of all assessed species.

We know that millions of species have already gone extinct over the long history of planet Earth. Biodiversity rates have always ebbed and flowed. In fact, at least 99% of all the organisms that have ever lived are now extinct. Researchers agree that five huge mass extinction events have already happened, including the one that wiped out the dinosaurs 66 million years ago.

However, extinction rates have been accelerating as human populations continue to grow, and many scientists argue we are living through a sixth mass extinction. This time, humans rather than natural events are to blame.

Species diversity in more than half of land ecosystems is now critically low.

A 10% drop is widely considered the threshold at which biodiversity's contribution to ecosystem services is compromised. It's estimated that over a quarter of Earth's land surface has already exceeded this safe limit.

Close-up of a butterfly wing

A sample from the wing of a Rothschild's birdwing, a large butterfly from Papua New Guinea. It's Near Threatened on the IUCN Red List, a resource which helps us track biodiversity levels.

Causes of biodiversity loss

Biodiversity is in trouble in the UK and across the globe, and its loss can refer to local and worldwide extinctions. Species and ecosystems can be fragile, so small changes can have large consequences.

The causes of biodiversity loss are complicated, and the human population is making the problems worse. Humans are increasingly disrupting the balance of biodiversity. Among the top drivers of biodiversity loss are land use change, exploitation of wildlife (through fishing, logging and hunting), pollution and our influence on climate.

We are overexploiting Earth's natural resources and converting natural habitats into farms, factories, roads and cities. In the ocean, we are overfishing, drilling and mining.

Cities and towns have a smoothing effect on biodiversity, tending to favour generalist species like feral pigeons. Those that require a particular habitat, or are intolerant of disturbance or pollution, often can't survive. This is called biotic homogenisation.

Animals and plants that can only live in one small area of land - like unique butterflies or flowers - can go locally extinct if the city's conditions are unfavourable to them.

Yellow lichen on a twig

This is a specimen of the lichen Xanthoria parietina on a twig. It's held in the crypt herbarium at the Museum. All living things, including plants and fungi, are represented by the word 'biodiversity'.

Biodiversity and invasive species

Animals and plants moving around the world are also big threats to biodiversity. When a new, non-native species arrives in an area, it is often called an alien species. Mostly this movement doesn't cause a problem. However, if that species causes harm to wildlife or humans, it is called an invasive alien species.

Invasive species are often introduced through human activity, either deliberately or accidentally. One example is rabbits in Australia, which were brought to Australia by human colonisers in the eighteenth century to be bred for food. Their population soon exploded and quickly caused devastation because of the huge amount of plants they ate.

Even now, rabbits in Australia can kill young orchards and cause serious erosion problems by eating trees and native plants.

This story is echoed all over the world. It is an especially big problem on islands, where wildlife has evolved in isolation over millions of years, and the ecosystem can be more vulnerable to the introduction of new animals and plants.

Invasive species can reduce biodiversity and species richness, cause extinctions and dramatically change ecosystems.

Protecting the natural world

Our future rests on a biodiverse Earth, so we can no longer take it for granted. We are now in an era when humans have a huge impact on the planet's natural systems.

Biodiversity loss is just as catastrophic as climate change, but the solutions are linked. Stopping further damage to the planet requires big change, but we can do it if we act now, together.

Every species matters, and the Museum is doing its bit to fight for biodiversity. Our scientists represent one of the largest groups in the world working on natural diversity and are at the forefront of digital, analytical and genomic technologies to expand our knowledge of nature.

Projects underway at the Museum are creating datasets that help us to understand ecosystem dynamics and changing patterns of biodiversity. The scientific research collections are crucial to understanding the unprecedented period of environmental change we're currently experiencing. They provide global information on 4.5 billion years of natural history on our planet and the last 300 years of environmental change.

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