A Snail With Anti-Cancer Properties & Fires In The Amazon

In 1758 the Swedish scientist Carl Linnaeus created and published the system still used to formally name and describe species. In the 253 years since, about 1.25 million species - roughly 1 million on land and 250,000 in the oceans - have been described and entered into central databases (roughly 700,000 more are thought to have been described but have yet to reach the central databases).

As of 2011, about 8.7 million (plus or minus 1.3 million) is the latest estimated total number of species on Earth - the most precise calculation ever offered - with 6.5 million species on land and 2.2 million in oceans.

One of those species, the Australian white rock sea snail (Dicathasis orbita) has just had a compound isolated from it which has not only antibacterial and anti-inflammatory qualities, but anti-cancer properties, preventing the formation of tumours in a colon cancer mouse model.

Colorectal cancer is the second leading cause of the 9.6 million cancer deaths every year, with the World Health Organization reporting 862,000 deaths in 2018.

Dicathais orbita. Credit: Flinders University

How many unknown species contain natural compounds that are valuable sources of future medicines for health, one wonders. And how many will disappear before we are able to investigate them?

If you are worrying how the fires currently burning in the Amazon rainforest will impact all these unknown species, well, yes the fires are destructive, and may contribute to further worsening the plight of some endangered species.

But one thing they are not doing is depleting Earth’s oxygen supply.

Scott Denning, professor of atmospheric science at Colorado State University writes:

“The resurgence of forest clearing in the Amazon, which had decreased more than 80% following a peak in 2004, is alarming for many reasons. Tropical forests harbor many species of plants and animals found nowhere else. They are important refuges for indigenous people, and contain enormous stores of carbon as wood and other organic matter that would otherwise contribute to the climate crisis.”

Some media accounts have suggested that fires in the Amazon also threaten the atmospheric oxygen that we breathe. French President Emmanuel Macron tweeted on Aug. 22 that

“the Amazon rain forest – the lungs which produces 20% of our planet’s oxygen – is on fire.”

The oft-repeated claim that the Amazon rainforest produces 20% of our planet’s oxygen is based on a misunderstanding. In fact nearly all of Earth’s breathable oxygen originated in the oceans, and there is enough of it to last for millions of years. There are many reasons to be appalled by this year’s Amazon fires, but depleting Earth’s oxygen supply is not one of them.

Nearly all free oxygen in the air is produced by plants through photosynthesis. About one-third of land photosynthesis occurs in tropical forests, the largest of which is located in the Amazon Basin.

But virtually all of the oxygen produced by photosynthesis each year is consumed by living organisms and fires. Trees constantly shed dead leaves, twigs, roots and other litter, which feeds a rich ecosystem of organisms, mostly insects and microbes. The microbes consume oxygen in that process.

Forest plants produce lots of oxygen, and forest microbes consume a lot of oxygen. As a result, net production of oxygen by forests – and indeed, all land plants – is very close to zero.The spiral in a snail's shell is the same mathematically as the spiral in the Milky Way galaxy, and it's also the same mathematically as the spirals in our DNA. It's the same ratio that you'll find in very basic music that transcends cultures all over the world.

There are four main reservoirs of oxygen on Earth: the terrestrial biosphere (green), marine biosphere (blue), lithosphere (Earth’s crust, brown), and atmosphere (grey). Colored arrows show fluxes between these reservoirs. Credit: Pengxiao Xu/Wikimedia, CC BY-SA

Even though plant photosynthesis is ultimately responsible for breathable oxygen, only a vanishingly tiny fraction of that plant growth actually adds to the store of oxygen in the air. Even if all organic matter on Earth were burned at once, less than 1% of the world’s oxygen would be consumed.

In sum, Brazil’s reversal on protecting the Amazon does not meaningfully threaten atmospheric oxygen. Even a huge increase in forest fires would produce changes in oxygen that are difficult to measure.

There’s enough oxygen in the air to last for millions of years, and the amount is set by geology rather than land use. The fact that this upsurge in deforestation threatens some of the most biodiverse and carbon-rich landscapes on Earth is reason enough to oppose it.”

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