Every 20,000 years, the Sahara Desert, one of the harshest and most inhospitable places on Earth, turns into a lush green grassland. I am not kidding! Primitive rock paintings and fossils have shown that Sahara was once a place where human settlements and a diversity of plants and animals thrived. The climate of North Africa swings between wet and dry climates every 20,000 years or so. This gives us periodic dry and green Sahara.

But why does that happen? What's the reason behind this transition? The answer is Earth's axial tilt. Right now, our planet is tilted at 23.5 degrees. However, this tilt is not constant. Instead, it varies between 22.1 degrees and 24.5 degrees over 41,000 years. When the Earth is tilted to receive maximum summer sunlight, it intensifies North Africa's monsoon activity, making for a wetter, "greener" Sahara. Conversely, when the planet's axis swings toward an angle that reduces the amount of incoming summer sunlight, monsoon activity weakens, producing a drier climate similar to what we see today.

The weather in the desert can be pretty treacherous. Sand and rocks heat up quickly during the day but do not keep the warmth at night. In addition, the air is dehydrated, so there are no water particles to slow down the temperature drop. Because of that, the average temperature in the desert during the day is 38℃, and during the night, it's -4℃. The highest temperature of 57.8℃ was recorded in 1922 in Libya, and the lowest reached -36 degrees in the mountains.

Despite harsh conditions, many life forms have their homes in the more hospitable regions of the desert. Most plants have reduced leaves and thick, water-rich stems. Animals aren't very colorful here. Light skin protects from overheating and helps with camouflage. Most species are active during nighttime and hide in caves and dens during the day. Camels, goats, gazelles, cheetah, and fennec fox make up the population of mammals. Ostriches also live in Sahara, alongside lizards, scorpions, and the famous venomous sand viper.

The Sahara's name comes from Arabic sahra, which means desert. The region played a vital role in the economy of ancient Africa. It made up many essential trade routes. For example, caravans of up to 12 thousand camels traveled between Egypt and Sudan, enabling the countries to exchange goods such as gold, copper, and salt.

Today, 2.5 million people live in the desert. Most of them live either in an oasis or nearby the rivers or lead a nomadic lifestyle, traveling across the desert with herds of sheep and goats.

Matmata in Tunisia is a famous town where some residents live in traditional underground homes. The place inspired the creator of Star Wars, George Lucas, and the hotel Sidi Driss was featured as a filming location twice.

Human activity affects the entire planet, and Sahara isn't an exception. There are tons of plastic on the shores of the desert. The mineral dust is an atmospheric aerosol composed of various minerals, oxides, and carbonates crucial for biogeochemical processes in every ecosystem. Sahara is the largest source of dust. However, scientists predict a 30% reduction in mineral dust within the next 20 to 50 years due to climate change caused by human activity.

It will negatively affect the quality of soils around the world. It may also have severe consequences for cloud formation, Arctic amplification, and Asian monsoons. Sahara keeps the most diverse ecosystems intact, and without it, we are all in danger.

Created by: Rishabh Nakra
Written by: Anna Sekścińska
Narrated by: Jeffrey Smith

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