Nature’s variety: Biodiversity explained

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Climate change has been well-publicised in recent months, with COP26 concluding last year in Glasgow, and heatwaves leading to record temperatures and drought this summer.

But what about its much less visible twin crisis: biodiversity loss? Though it’s harder to spot, biodiversity loss continues, and governance of the issue is currently undergoing major revision globally, and in Scotland. The Scottish Government has just concluded its consultation period on the next iteration of Scotland’s Biodiversity Strategy. The strategy aims to address the biodiversity crisis (sometimes also known as the ecological crisis).

This is the first of a two-part blog on biodiversity. This blog explores what is meant by biodiversity and biodiversity loss. Part two looks at ongoing changes to biodiversity policy globally and in Scotland, and the role of the Scottish Parliament in scrutinising this challenge.

What is biodiversity?

Scotland is home to an estimated 90,000 species. 

Biological diversity – biodiversity – is the variety of life on earth, including genetic variety within species, variety between species, and the variety of ecosystems – or natural communities – that make up the earth

Graphic illustrating the different levels of biodiversity. Genetic diversity within species, the variety of different species, and the variety of ecosystems all make up biodiversity.
Biodiversity includes genetic diversity within species and variation between species and ecosystems. Source: SPICe

Biodiversity is not just made up of discrete components (such as a given number of different species) but also includes ecological interactions in the natural environment, delivering the natural stocks and flows that underpin ecosystem services. Ecosystems services are the things that nature provides, such as air quality, water purification, pollination, food, timber, and recreation. This makes biodiversity difficult to measure – because it is composed of a vast number of interlinked, interacting components.

What is biodiversity loss?

The world is experiencing a rapid decline in the variety of life on earth – this is what is meant by biodiversity loss.  A global study carried out by IPBES (the Intergovernmental Science-Policy Platform for Biodiversity and Ecosystem Services) was published in 2019 and was the most comprehensive assessment of the earth’s biodiversity to date. The Global Assessment Report concluded that:

  • 75% of the land surface and 66% of the ocean area has been significantly altered by humans while more than 85% of wetland area has been lost.
  • An average of around 25% of species in assessed animal and plant groups are threatened with extinction (around 1 million species in total).
  • Average abundance of native species in most major land-based habitats has fallen by at least 20%, mostly since 1900. Threats of extinction are most likely increasing.
  • Wild (non-domesticated) species genetic diversity has been declining by roughly 1% per decade since the mid-19th century. Wild mammal and amphibian genetic diversity tends to be lower in areas where human influence is greater.

These findings have led some scientists to conclude that the world is experiencing a sixth mass extinction event, with an “exceptionally rapid loss of biodiversity over the last few centuries”.

In Scotland, a 2019 report on the ‘State of Nature’ concluded that between 1994 and 2016:

  • 49% of Scottish species have decreased
  • 28% have increased

Of species assessed, 11% have been classified as threatened with extinction.

What causes biodiversity loss?

Biodiversity loss is caused by a number of different factors. NatureScot identifies five key drivers of biodiversity loss in Scotland:

  • Changing use of land and sea: how we use land and seas for food, materials or infrastructure affects biodiversity. This is the biggest driver of biodiversity loss.
  • Use of natural resources: for example, how we harvest fish, wood and other organisms or materials from the wild.
  • Climate Change: climate change is causing major changes to the natural world. For example, warming temperatures might make a species’ native home less suitable, or more suitable for new pests or diseases, which can pose a threat.
  • Pollution: This can range from anything from particles emitted from vehicles or machinery to plastic litter.
  • Invasive non-native species: as humans move around the world, they sometimes bring non-native species with them on purpose, and sometimes they hitch a ride by accident. Introducing non-native species can have far-reaching consequences for native biodiversity. For example, rhododendron, though often planted for its beautiful flowers, can interfere with the ability of a site to regenerate, leading to a reduction in biodiversity. According to Forest Research, it has been shown to reduce the number of earthworms, birds and plants on a particular site.

NatureScot also includes ‘indirect drivers’ on its list of key pressures, such as a lack of value or recognition for the importance of biodiversity, and a disconnect from nature.

Pressures can affect biodiversity in different ways, for example:

  • Habitat: Pressures might reduce native habitats of particular species (i.e. by converting land for other uses), or make habitats less optimal (i.e. through pollution, climate change, or the introduction of non-native species).
  • Food: It might affect the source of food and nutrients for plants and animals. Pollution can affect the nutrient balance of the soil, invasive non-native species might compete for food, or climate change, fishing, or land management might make key food sources for a species less available.
  • Reproduction: Pressures may disrupt a species’ ability to reproduce. There may be changes in their usual breeding grounds or less food, water or nutrients available which might make it harder for offspring to survive.

The second part of this series will explore ongoing developments in biodiversity policy which aims to address some of these issues.

Key resources

Anna Brand, Senior Researcher