The Amazon Rainforest is a moist broadleaf forest that covers 5.5 million square kilometers (1.4 billion acres) of the Amazon Basin which totals 7 million square kilometers (1.7 billion acres). Over half of the rainforest is located in Brazil but it is also located in other South American countries including Peru, Venezuela, Ecuador, Colombia, Guyana, Bolivia, Suriname and French Guiana. The Amazon represents over half of the planet’s rainforests, comprising the largest and most species-rich tract. It is home to half of all life on the planet.
It’s also commonly said that “the Amazon Rainforest is the lungs of the planet, producing 1/4 of Earth’s oxygen. Yes and no. Being such a huge aggregation of plants (making oxygen through photosynthesis), it does produce 20 times more oxygen than humans need. But none of the oxygen leaves the Amazon, because all the animal life there uses it among themselves. Nevertheless, the Amazon is critically instrumental in the larger process, indirectly supporting oxygen production. The process starts in Africa, in a place called the Bodélé Depression of the Sahara Desert.
10,500 years ago, a 5000 year period of monsoon rains over the Sahara Desert transformed the region into lush and habitable savanna. A number of low areas became lakes, and as with other bodies of water, there flourished an organism, four times thinner than a human hair, called a diatom, a type of phytoplankton. Each diatom lives only six days, yet they amass in vast numbers by doubling their population every 24 hours. After each boom-bust cycle, billions of dead diatoms settle to the bottom of oceans or seas, accumulating in thick layers. The key to future oxygen cycles lie in two essential minerals in the diatoms’ “skeletons” – phosphorous and iron – Saharan Dust Feeds Amazon’s Plants, and The Amazon Rainforest Gets Half Its Nutrients From a Single, Tiny Spot in the Sahara.
The Bodélé Depression in central Chad is an ancient dried up seabed, consisting of millions of tons of dead diatoms. From this site, and others in the Sahara, strong winds pick up 182 million tons of diatom dust each year and carry it across the Atlantic Ocean, where rains deposit about 72 million tons of it over the Amazon basin. The diatom-laden rain fertilizes the Amazon forest with phosphorous, replenishing the supply of this essential mineral which had leached away over the previous year. In turn, the rainforest trees transevaporate moisture from the soil up through their leaves. For example each Brazil Nut Tree, one of what are called “super trees”, lifts 260 gallons of water into the air daily – The Amazon’s Brazil nut tree creates its own rainfall — and it’s in danger. Each morning, a huge upward torrent of fog emanates from the treetops, condensing as it cools to form clouds. These rain clouds head west, encounter the Andes, and release the rain, which leaches phosphorous from the soil and carries it to the ocean to nourish the growth of diatoms.
The last stage of oxygen production is triggered by trace amounts of iron carried in the African diatom dust. Much of the deep ocean is devoid of iron, making it blue, while iron-rich coastal waters are green with biological growth. Iron is a limiting factor for plant metabolism, and diatoms need iron to photosynthesize and make oxygen. The dust from the Bodélé Depression contains iron, and only trace quantities are needed. The amount of iron needed in a ton of water would weigh about as much as a single eyelash. Between 71% and 87% of the iron in seawater samples originated in dust storms from the Sahara desert, enabling the diatoms to flourish and produce oxygen – Desert Dust Feeds Deep Ocean Life.
Unfortunately, as with other oceanic organisms, warming ocean temperatures due to climate disruption slow the growth of diatoms. The primary function of diatoms are as phytoplanktons making oxygen. Most data sources attribute 50% of the oxygen on Earth to diatoms, though some estimates are even higher. However, a study done at the University of Leicester has shown that if ocean temperatures rise around six degrees Celsius, oxygen production by phytoplankton could cease by disrupting the process of photosynthesis. The study’s lead analyst said “About two-thirds of the planet’s total atmospheric oxygen is produced by ocean phytoplankton, and therefore cessation would result in the depletion of atmospheric oxygen on a global scale. This would likely result in the mass mortality of animals and humans” – Failing phytoplankton, failing oxygen: Global warming disaster could suffocate life on planet Earth.
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