Biodiversity tries to measure the variation among organisms in a community or ecosystem. But how is biodiversity measured? Is there a single best way to measure biodiversity?
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The Biological Diversity Rules have laid down the process of establishing the three-tier structure of biodiversity resource regulation at the national, state and local level. (Representative image)
— Siddharth Bharath
(The Indian Express has launched a new series of articles for UPSC aspirants written by seasoned writers and erudite scholars on issues and concepts spanning History, Polity, International Relations, Art, Culture and Heritage, Environment, Geography, Science and Technology, and so on. Read and reflect with subject experts and boost your chance of cracking the much-coveted UPSC CSE. In the following article, Dr. Siddharth Bharath simplifies biodiversity and discusses its significance by linking the concept to everyday life.)
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Imagine this: You look out onto a busy city street, and everyone looks exactly the same. They speak in the same voice. They all have the same actions and mannerisms. They wear the same clothes. This would feel very strange. We intuitively know that this situation cannot happen in a city because no two people are the same.
We live in a world of endless variety. That is true among humans, and among all living things. We use the word biodiversity to describe that variety. Let’s explore biodiversity, its importance, ways to measure it, and, in doing so, celebrate some of the beauty and wonder of our natural world.
What is biodiversity
Understanding how biodiversity sustains us is crucial for our own well being. All of the diversity of the life we see on our planet has evolved over millions of years. We have evolved alongside them – the plants and animals that provide us with food and medicine, the bacteria in our gut that do a lot of our digestion, and the fungi that break down and recycle wastes back into the ecosystem. The rich variety of life makes ecosystems function.
In addition to all the tangible ways that nature contributes to our well being, there are a whole host of intangible contributions – beauty, inspiration, relaxation, culture – that come from biodiversity for us.
The United Nations Convention on Biological Diversity defines biodiversity as: “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: this includes diversity within species, between species and of ecosystems.”
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Biodiversity tries to measure such variation among organisms in a community or ecosystem. It can be measured in different ways, using different metrics.
We would never expect that class, caste, gender or any single axis of difference in humans would fully explain the diversity of life experiences present in a group of humans. That view would be simplistic and naive, and the same is true for biological life.
In fact, no single way of measuring biodiversity is the best, rather we have to choose which measures to use in each situation. Let us try different ways of measuring and categorising the differences between people in a busy city, and see how that relates to biodiversity.
We can group people by their ancestry – trace parents and children across generations. A century ago this would be done by documenting actual lineages, but today it can be done by analysing DNA. The scientific term for this is phylogeny.
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You can analyse certain regions of DNA that change very slowly and are common to nearly all life. This results in a tree of life – with organisms that are closer together having a common ancestor more recently than organisms that are far apart.If we measure the diversity of life in a group by this method, we get phylogenetic diversity (also called genetic diversity). This kind of diversity is intuitive to describe but is quite complex to operationalise into a measure.
We can also group people by occupation – performing different roles within the society. A small village might have fewer occupations present, and many people will be performing multiple roles. A large city will have people who are able to devote their full time to very specialised occupations. This diversity of occupations is called functional diversity (or ecological diversity).
Functional diversity in biology measures how different organisms are in terms of what they are doing in their environment and interacting with other organisms. For example, compare two communities of insects that we find on two different patches of forest floor. Community A has dung beetles, yellow dung flies and two species of millipedes. Community B has dung beetles, a ground nesting bee, crickets and one species of ant.
Community A only has species that are very similar in function, they all eat animal dung and decompose material on the forest floor. Community B consists of insects that perform very different activities. So while both communities have four species each, B is more functionally diverse than A. These two ways of measuring diversity, while easy to define, are not the most commonly used.
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Species diversity, the number of biological species in a given area or group, has been the most common measure of biodiversity for a long time. Species are defined in different ways based on which kind of organisms you are dealing with. For animals, one easy definition has been that individuals of two different species cannot mate and produce fertile offspring.
For microorganisms like bacteria, the definition is based on their genetics. When you zoom into it, the borders of definition of a species are not completely clear. It is a categorisation that we make for our convenience. Much like how two states or two nations might seem very different, but when you zoom into the border between them, you realise there is a lot more similarity between the two groups of people living on opposite sides of the border. The border is a negotiated construct, much like species are.
Each of these three ways of measuring diversity detailed above can be expressed by different numbers. For example, species richness is just the count of how many different species are in an area.
Consider a community of 100 plants, where there are 10 plants each of 10 species, it has a species richness of 10 (think of a vegetable patch containing 10 different vegetables and greens). A second community of 100 plants, with 91 of one species, and 1 each of 9 other species, also has a species richness of 10 (think of a field of mostly wheat plants with a couple of weeds growing around the edges).
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The second community is far less diverse than the first, but species richness doesn’t capture that difference. Ecologists have developed many metrics that combine both richness and abundance of species to give better measures of the diversity of a community. The same carries over to measures of functional diversity and phylogenetic diversity, though those are a little less intuitive to understand for a beginner.
Most people would find the measures discussed above quite abstract. Popular discourse about biodiversity tends to focus on one or a few species in each ecosystem, using their presence as a proxy for the health of a whole ecosystem. There are a couple of different concepts that do this.
Species shaping ecosystems
Governments, conservation agencies and the media pick a few charismatic species to frame conservation efforts – tigers, elephants, pandas, peacocks, rhinoceros, orangutans etc. These are often called flagship species for biodiversity, using the name of one species to try and support whole ecosystems where they are present.
However, flagship species are essentially the models picked by the marketing department for advertisements about a company, not the actual workers, engineers or scientists who are actually doing the work of the company.
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Keystone species are those whose impact on an ecosystem is disproportionately large compared to its abundance. It is named like the small keystone in an arch which is crucial to keeping the arch from falling. For example, pollinators like bees are crucial to the reproduction of many different plant species.
Ecosystem engineers refer to species that significantly change the structure of the ecosystem, and which other species depend on. Termites are ecosystem engineers in savannahs, changing the abundance and regularity of trees that are present.
Indicator species refer to species whose presence shows the health of the ecosystem. Lichen growing on trees are quite sensitive to air pollution, and therefore their presence indicates that the air is relatively clean in an area.
Invasive species are species that are not “originally” from an area but are spreading rapidly and displacing local species. Lantana camara, an ornamental shrub brought by the British to be a garden plant, is invasive in huge areas of the Western Ghats, completely taking over the forest understory.
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However, each of the above categories is also a measure of convenience, and is problematic in many ways. The presence of a keystone species doesn’t mean an ecosystem is in good shape, and the presence of invasive species doesn’t automatically mean things are bad. Understanding biodiversity and ecosystem health is complex, and it’s important to know and respect the proxies that we are using to do so.
Post Read Question
Understanding how biodiversity sustains us is crucial for our own well being. Comment.
How would you go about measuring the diversity of plants in a forest, as compared to a nearby agricultural field?
What are some concepts that show species that disproportionately shape ecosystems? Critically analyse with examples.
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(Dr. Siddharth Bharath is an ecologist, educator and entrepreneur based in Bengaluru. He works with Swissnex in India.)
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US President Donald Trump on Monday said the United States is “close to signing a trade deal” with India, after announcing new reciprocal tariffs on 14 countries — including Bangladesh, Malaysia, Japan, Cambodia and South Korea — setting rates at 25 to 40 per cent, and warning that rerouting foreign goods or retaliating would attract even higher US tariffs.
This comes as Indian negotiators are understood to have offered substantial market access to US products in most sectors, excluding sensitive areas such as dairy and agriculture. The US, in turn, is expected to offer lower tariffs on labour-intensive sectors such as textiles and footwear.
