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What is biodiversity and why is it important?

Here Martin explains biodiversity. Dr Matthias Schmidt Thomsen then discusses why it is important and the potential consequences of biodiversity loss.

Biodiversity (short for biological diversity) is the variety and variability of biological life across the world. It refers to the number and abundance of species present within a given habitat or ecosystem and is made up of 3 interwoven factors: Ecosystem diversity, species diversity and genetic diversity.

Biodiversity is not constant across the world. The distribution and abundance of species varies globally and within regions. Broadly speaking biodiversity is highest in the tropics and declines as we move towards the poles. There are various factors that influence the distribution of biodiversity. These include environmental factors such as temperature, depth, freshwater input, organic input and sediment type, as well as biological factors such as how species interact with each other (e.g. predation). The 2010 Census of Marine Life project catalogued and mapped biodiversity across the world’s oceans. You can see a depiction of this in the image below. The colour scale shows increasing marine biodiversity from blue (low biodiversity) to red (high biodiversity).

A global map with a grid overlay. Grid boxes are colour-coded according to level of diversity, with blue (lowest diversity) zones in the polar regions and red (highest diversity) zones located in the western Indian and eastern pacific oceans, and around the coasts of India and South Africa.Map of marine biodiversity. © Tittensor et al., Nature (2010).

High species diversity is important for the processes and functions of all ecosystems, whether terrestrial or marine, mountain top or deep sea trench. This is because biodiversity is good at packaging nutrients, energy, matter and information, and transferring it between compartments. An example of this can be seen in the carbon cycle.

All species, whether plants, animals, or microscopic organisms, are integral to regulating a variety of ecosystem processes and functions, which in turn sustain goods and services that humans rely on. These include providing clean air, food, pollination of crops and the regulation of pathogens, all of which are imperative for human standards of living and well-being.

However, the provisioning of these goods and services is threatened by the current rates of species loss, sometimes also referred to as the crisis on biodiversity or the sixth mass extinction (in Earth’s history). Given the role that species play, a decline in diversity may have serious consequences for many of the major processes that our ecosystems rely on.

The reason species may go extinct are varied and complex. Species differ in sensitivity and therefore have different tolerances to environmental stressors depending on the type (e.g. trawling, plastic, heavy metal pollution, ocean warming and acidification), duration (press, pulse) intensity of stress (high, low) they experience.

The worst case scenario would be random extinction events, where any species can go extinct at any time. However the reason species tend to go extinct is due to specific circumstances, such as physical disturbance, changes in environmental conditions, introduction of competing species or habitat loss. However it’s not all doom and gloom as some species do respond to change in positive ways.


Examine the world map of marine biodiversity near the top of this step. Is it what you expected to see? Is there anything about the distribution of biodiversity that surprised you?

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