In the poignant documentary David Attenborough: A Life On Our Planet, which recently aired on Netflix, the planet’s favorite naturalist drew harrowing comparisons between the 1986 Chernobyl disaster and the ongoing crisis of biodiversity loss on Earth. Speaking from the condemned city, Attenborough describes how, without proper intervention, the climatic and ecological consequences of biodiversity loss could one day parallel the destruction caused by the rupture of Chernobyl’s radioactive core and recent research indicates that we are already reaching a critical point.

New research published in the journal Proceedings of the Royal Society B has reported that populations of coral of all sizes have seen a 50 percent reduction on the Great Barrier Reef in the last 30 years. The study looked at corals across the length of the Great Barrier Reef, gathering data on their populations between 1995 and 2017. Analyses of the results revealed a sharp depreciation in corals since the 1990s in both shallow and deep-water species. The losses were most pronounced among the coral species that suffered from mass bleaching events triggered by record-breaking ocean temperatures in 2016 and 2017.

Since the close of the study's data capture in 2017, there have been further records smashed in the waters surrounding the Great Barrier Reef, as a spike in ocean temperature kicked off its third and most widespread bleaching event to date earlier this year.

"We measured changes in colony sizes because population studies are important for understanding demography and the corals' capacity to breed," said lead author Dr Andy Dietzel, from the ARC Centre of Excellence for Coral Reef Studies (CoralCoE) in a statement. "A vibrant coral population has millions of small baby corals, as well as many large ones — the big mamas who produce most of the larvae.”

These findings tie in with the overarching message of Attenborough’s latest release, which is that if climate-driven biodiversity loss is left to run rampant we may lose the critical ingredients required to restore ecosystems such as the Great Barrier Reef to a healthy and functional condition. With fewer large breeding adults and fewer baby corals to take their place, the resilience and capacity to recover even the world's largest reef is thrown into question.

The documentary is accented with chronological updates regarding population, biodiversity loss, and atmospheric carbon, the latter of which climbs throughout Attenborough’s life starting at just 280 parts per million (ppm) in 1937 and eventually reaching a grim crescendo in 2020 of 415ppm. He explains how the fossil record reveals that a spike in this air pollutant has “always been incompatible with a stable Earth,” with peaks featuring in all the mass extinction events. In the past, it took volcanic activity a million years to reach tipping point, but by dredging up and burning millions of years' worth of living organisms in the form of fossil fuels like oil and coal, we’ve managed to achieve the same damage in less than 200 years. So, is the next mass extinction event on the horizon?

Climate scientists warned that increasing atmospheric carbon would push up global temperatures, which remained stable until around 1990. It was later discovered however that this was due to the ocean’s ability to absorb the carbon we were churning out, a safety clause that ended when both air and ocean temperatures began to climb before the millennium. We know that coral bleaching happens in response to rising ocean temperatures, as the heat triggers the corals to expel the algae that live symbiotically on their surface, leaving only white, bone-like structures.

“When you first see it you think, "perhaps it’s beautiful," and suddenly you realize it’s tragic because what you’re looking at is skeletons,” Attenborough says. “Skeletons of dead creatures.”

As well as losing the protection of the ocean as an effective carbon sink for our emissions, we’re increasingly at risk of a drastic increase in global temperature as a result of the ever-decreasing ice caps in both the North and South poles. These enormous ice sheets act as a reflective surface sending much of the Sun’s energy back into space. Without them, our already warming planet will take in that extra heat, and our sea levels will rise to an extent that threatens both human and wildlife populations. The effects of melting ice caps are already being seen among animals such as polar bears, which currently face extinction by 2100 due to melting sea ice. 

Furthermore, as long-frozen landscapes thaw they release copious amounts of methane, the disastrous greenhouse gas that is associated with cattle farming and has the potential to trigger a huge spike in global temperature. In the documentary, Attenborough explains how average temperatures have increased by 1°C (1.8°F) in his lifetime alone, and makes grim projections for where the planet could see itself in 10, 20, and 30 years as well as at the turn of the century if more isn’t done to prevent climate change.

But, he grants us, there is hope. In order to turn the tide on rising global temperatures, drastic changes need to be made regarding both our use of and occupation in the natural world. For starters, rewilding spaces now occupied by cities, farms, and suburbia could increase available plant life that can absorb harmful carbon dioxide and pump it back out as oxygen. Rewilding in farms has seen success in examples such as Knepp Wildland in the UK, and recent research published in the journal Nature has described how restoring just 30 percent of ecosystems could prevent 70 percent of predicted extinctions, protecting Earth’s biodiversity. 

Eating a more plant-based diet will also have great environmental benefits, reducing harmful emissions from livestock, which are a big source of methane, and freeing up farmland that left to return to a wilder state could both transform carbon dioxide and support more diverse ecosystems. A Life on Our Planet highlights how the Netherlands is paving the way for more sustainable agricultural practices, using hydroponic farms to increase yield while reducing demands for land, water, and harmful pesticides. And, of course, the integration of greener energy sources also earns a special mention in the documentary, with sunlight, wind, water, and geothermal energy each getting a shout out. 

The issue of returning Earth to a sustainable state of being is as complex as it is pressing. While it’s upon each of us to do our part in redressing the balance on climate change there still remain big barriers regarding the reluctance of industry and governments worldwide in tackling the few who constitute the greatest contributors to greenhouse gas emissions.

However, as Attenborough concludes in the documentary, this shouldn’t distract us from the opportunity we still have to turn the tide on the climate crisis, support biodiversity and in turn save our own species by creating a sustainable planet enriched with plant, animal, and human life.

To use the icon's own words, “Just imagine that.”