A brief history of biodiversity and our current crisis

A brief history of life

About 4.5 billion years ago, the Earth formed as a hot ball of rock. In 100 million years, that rock cooled enough for water to condense and the oceans were formed. It took a billion years before the first living cells came about in the oceans. These bacteria were all there was for another billion years. During this time they achieved a whole range of innovations that fundamentally altered and made the Earth we live in. 

Around 2.7 billion years ago, photosynthetic bacteria, specifically cyanobacteria, first became abundant in the oceans. These organisms captured energy from sunlight and converted it into chemical energy to fuel their growth. A byproduct of this reaction was Oxygen, a very reactive gas that was barely present in the atmosphere of the young Earth. 

Over the next 300 million years, oxygen made up about 10 per cent of the Earth’s atmosphere. The period, marking the rise of oxygen in the early Earth’s atmosphere, is often referred to as the Great Oxidation Event or the Oxygen Catastrophe. This huge change eradicated many of the existing organisms that could not survive in an oxygen rich atmosphere.

Multicellular life

Organisms with more than one cell (multicellular life) evolved only around 2.1 billion years ago. Half of the history of the planet had already passed by then, and that story was entirely made of single cells. 

Since then, life has diversified and developed to cover all of the earth. Over millions of years, living things adapted to different environments and created new environments, resulting in a great diversity of organisms. However, there have been some periods of great environmental change or catastrophic events that wiped out a lot of the life on the planet. 

These are called mass extinctions and over five of them have happened in the last 500 million years. These mass extinctions have been variously attributed to such phenomena as environmental changes, volcanic activity, and asteroid impacts.

The most recent mass extinction happened 66 million years ago, which is famous for ending the reign of the dinosaurs.

A massive asteroid hit the earth near present day Mexico, resulting in a crater approximately 200 km in diameter that is visible today. During this event, around 75 per cent of all plant and animal species went extinct, including all of the non-avian dinosaurs. 

That extinction created the opportunity for mammals to fill the ecological space left by the dinosaurs, leading to the world we live in today. Birds are the only descendents of dinosaurs left in the world today.

We are witnessing a mass extinction today

We are currently living through what many experts describe as a sixth mass extinction. Species are vanishing at rates estimated to be 100 times higher than the natural rates of extinction that prevailed in the previous 20,000 years. This is happening primarily due to human activities.  

Increasing carbon levels in the oceans may lead to the sixth mass extinction in Earth’s history by about 2100, MIT scientists have predicted after analysing data from the last 540 million years. (Image Source: MIT)

Over the past 200 years, we have greatly accelerated our usage of the earth’s energy and resources to drive our growing economy and population. There were 1 billion humans on Earth in 1804. 220 years later, our population stands at 8.17 billion in 2024. If we measure the mass of all the mammals on earth, we find that livestock makeup around 62 per cent, humans about 32 per cent, and wild mammals only account for 4 per cent. 

Why does it matter if species vanish from our planet? Nature contributes directly to so many aspects of human society and economy – clean air, clean water, nutrition, fuel, healthcare  and much more. Declines in biodiversity, even when it is of species that we don’t directly depend on, reduces the ability of ecosystems to function.

What happens when we lose biodiversity

Let’s explore this through an analogy that compares a biological community to a human company, where we think of each species as being one employee of the company.

A large company starts losing employees at random. A mid-level manager leaves. There is chaos in their team for a while, but then one of the junior members manages to get things under control and takes the manager’s position. Sometimes when one species is lost, another similar species is able to take up its role in the ecosystem.

A janitor leaves, and his colleagues do a little more work to cover his shift. But if half of the janitors leave, then cleanliness really suffers, and the offices are going to become difficult to work in. If too many species in a particular functional role are lost, that function gets compromised.

An office clerk leaves. His/her job seems redundant, there are others who can easily step in. But soon we find that he/she was the centre of the friendship network of the office. It shows how the loss of a seemingly minor role can affect the whole system. There is a lot we don’t know about species and ecosystems. Similarly, if the CEO leaves, the company rapidly loses coordination and productivity, just like losing a keystone species can have a huge impact on an ecosystem.

Just like any human organisation, biological communities are sustained by a web of connections.

Unlike a company there isn’t an intentional design behind the structure – ecosystems are complex systems that form following the rules of nature, rules that scientists are still trying to find out even while ecosystems are vanishing in front of our eyes.

Major drivers of our current biodiversity crisis 

The Intergovernmental Platform on Biodiversity and Ecosystem Services, in their 2022 report, lists five direct anthropogenic drivers of biodiversity change – (i) Pollution, (ii) land/sea use change, (iii) direct exploitation and extraction of resources, (iv) climate change, and (v) invasive alien species. 

These direct sources of change are being caused by more diffuse and indirect drivers such as institutions (formal and informal), economic drivers, technological drivers, governance drivers, conflicts and war, sociocultural and socio-psychological drivers (such as values, beliefs, norms and education). Let’s go into some more detail about the direct drivers.

(i) Pollution – It has reshaped the world we live in over the last 200 years. Excess fertiliser used in agricultural fields gets carried into water bodies and kills or alters a lot of the life in lakes. Direct dumping of effluents from industries into water bodies causes a lot of harm to humans and non-humans. 

Industrial accidents, such as the Union Carbide disaster that happened in Bhopal in 1984, contaminate air, land and soil in a way that affects families for generations. Communities near the disaster site in Bhopal are still drinking contaminated water, 40 years after the disaster.

(ii) Land and sea use change – It is one of the biggest contributors to both climate change and biodiversity loss. Forests in the tropics are being cleared to create farmlands or pastures for livestock. Many governments treat expansion of oil palm plantations in forest regions as not deforestation, because they are creating a landscape with trees (albeit one that is hugely different from a natural forest). 

Deep sea trawling is essentially the same as clear-cutting a forest on land, as trawlers destroy sensitive ecosystems and release a lot of carbon dioxide from organic matter that is settled on the ocean floor. Only 17 per cent of the land area of the world has been designated for protection by different countries, and even worse, just 2.7 per cent of the ocean is designated as marine protected areas.

Many ecosystems are suffering greatly from humans over extracting or over exploiting them. A study from 2017 estimates that 34 per cent of all global fisheries are overexploited, and an additional 60 per cent will be there very soon. Because fish are mostly invisible to us, and the oceans are not under the jurisdiction of any country, regulation of overfishing has been a huge challenge.

(iii) Climate change – It is also causing a lot of species to go extinct. Species in cold environments, like polar regions and mountains, are finding the world becoming too warm. Species in warmer areas face risk of drought or overheating. This is especially true of insects, as many insect species in the tropics have a low threshold for heat compared to other animals. The changing climate is also complicating diseases and invasive alien species. Many pests and diseases that couldn’t survive winter in cold areas are not hindered any more by the relatively mild winters, and therefore increasing in incidence. 

The road ahead

When discussing biodiversity we often think of nature as being far away from us, inside the deep jungle. But nature is all around us. Cities, towns and even a single tree canopy can be a diverse space. Before we attempt to conserve species, do you even know who all live outside your window? Challenge yourself to identify 15 bird species around you in the next week. I guarantee you that they are there waiting to be discovered!

The state of biodiversity in the world today is dire, and the response of the global community to this has been much slower and less organised than the response to climate change. This could be in part because biodiversity loss has been harder to define and measure as compared to climate change. The narrative and action around biodiversity conservation is now growing as the scale of the current crisis becomes apparent to everyone. 

Post Read Questions

The most recent mass extinction happened 66 million years ago, which wiped out the non-avian dinosaurs. How did it lead to the rise of mammals and the current biodiversity we observe today?

What is the Great Oxidation Event? How did the influx of oxygen into the Earth’s atmosphere affect the planet’s early life forms?

Many scientists have warned that we are currently in the midst of a sixth mass extinction. Critically analyse the human activities that have accelerated extinction rates.

What are the five direct drivers of biodiversity change identified by the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) in its 2022 report. How do they impact ecosystems?

(Dr. Siddharth Bharath is an ecologist, educator and entrepreneur based in Bengaluru. He works with Swissnex in India.)

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