Ikigai Daily
Menu
WonderBiodiversity monitoring fact

Environmental DNA, or eDNA, is the genetic material that animals and plants shed into water, soil and air. By collecting and testing it, scientists can find out which species live in a place without seeing or catching any of them.

Environmental DNA

BiologyNatureScience

The story behind the card

Animals and plants constantly shed skin cells, scales, mucus, pollen and waste. Researchers filter a water sample or collect soil, extract the DNA and test it, either for one target species or for short, telltale DNA sequences that identify many species at once. The method finds rare, shy or invasive species with little disturbance. In June 2018 a team led by the geneticist Neil Gemmell sampled the water of Loch Ness in Scotland; they found no reptile DNA at all, but a great deal of eel DNA. A positive result is not a headcount, though: DNA drifts with currents, breaks down over time and can contaminate samples, so results still need careful interpretation by ecologists.

Türkçe oku
Çevresel DNA, canlıların suya, toprağa ve havaya bıraktığı genetik izlerdir. Bilim insanları bu izleri toplayıp inceleyerek bir yerde hangi türlerin yaşadığını, hiçbirini görmeden ya da yakalamadan öğrenebilir.

Hayvanlar ve bitkiler durmadan deri hücreleri, pul, mukus, polen ve dışkı bırakır. Araştırmacılar bir su örneğini süzer ya da toprak toplar, içindeki DNA'yı ayırır ve ya tek bir türü arar ya da birçok türü aynı anda tanıtan kısa DNA dizilerine bakar. Yöntem nadir, ürkek ya da istilacı türleri onları rahatsız etmeden bulmayı sağlar. Haziran 2018'de genetikçi Neil Gemmell'in yönettiği bir ekip İskoçya'daki Loch Ness Gölü'nden su örnekleri aldı; hiç sürüngen DNA'sına rastlamadı, ama bol miktarda yılan balığı DNA'sı buldu. Yine de olumlu bir sonuç hayvanların sayısını vermez: DNA akıntıyla taşınır, zamanla bozulur ve örneklere bulaşabilir. Bu yüzden sonuçları ekologların dikkatle yorumlaması gerekir.

Sources and further reading

Background reading: Environmental DNA
Get the mobile appAbout our cards

Related cards

These cards share a subject or reading mode with the card above.

WonderNature

Welwitschia, a plant of the Namib Desert in Namibia and Angola, grows only two leaves in its whole life. They keep growing from their base for centuries, and some plants are thought to be more than a thousand years old.

The Austrian botanist Friedrich Welwitsch came across the plant in southern Angola in 1859; he wrote that he knelt and gazed at it, half afraid that touching it would prove it imaginary. It is a gymnosperm, like conifers, which means its seeds form in cones rather than inside fruit, and male and female cones grow on separate plants. Over the years the wind tears the two leaves into many ribbons, so an old plant looks like a heap of leaves. The Namib is one of the driest places on Earth. The leaves catch fog and dew, which drip onto shallow roots, although a 2019 study suggests that rain soaking into the ground is its main water source. The plant appears on Namibia's coat of arms.

WelwitschiaRead card
WonderNature

The kākāpō, a flightless, night-active parrot of New Zealand, courts with sound: in the rare years when it breeds, males dig shallow bowls in the ground and boom from them through the night, a deep call that can carry for more than a kilometre.

The kākāpō is the world's only flightless parrot and the heaviest, with males weighing up to about 4 kilograms. It once lived across New Zealand, but hunting and the dogs and rats brought by Polynesian settlers, then the cats, stoats and rats that came with Europeans, drove it close to extinction. Today every surviving bird has a name and lives on predator-free islands or in fenced sanctuaries, watched over by the Kākāpō Recovery programme. Females breed only in years when rimu and some other native trees produce a huge crop of fruit, known as masting, which comes every two to four years. In those seasons rangers check nests closely and sometimes raise chicks by hand.

KākāpōRead card
WonderNature

Great frigatebirds can sleep while soaring over the ocean, sometimes with one half of the brain and sometimes with both. In flight, though, they sleep only about 40 minutes a day, against more than 12 hours a day on land.

The finding comes from a 2016 study led by Niels Rattenborg of the Max Planck Institute for Ornithology in Germany. His team fitted great frigatebirds nesting in the Galápagos Islands with small devices that recorded brain activity during flights lasting up to ten days. Most sleep came in bursts of about twelve seconds, often while the birds circled upward in rising warm air. When only one half of the brain slept, the eye linked to the awake half usually looked in the direction of flight. Frigatebirds hunt far out at sea, yet their feathers are not waterproof, so they cannot rest on the water. How they cope with so little sleep is still not known.

Great frigatebirdRead card
StillnessNature

Biological soil crusts are living communities of cyanobacteria, lichens, fungi, mosses and algae that bind dryland soil and influence water and nutrient cycles.

Scientists often call these crusts biocrusts. The cyanobacterium Microcoleus vaginatus is usually among the first to settle: its sticky filaments glue sand grains together and prepare the ground for the lichens, mosses and algae that follow. Some crust organisms also fix nitrogen, taking it from the air and turning it into a form plants can use, which matters in poor desert soils. Growth is slow in dry ground, so a crushed crust can take years to regain its first layer and decades or even centuries to rebuild fully. In US national parks on the Colorado Plateau, such as Arches and Canyonlands, signs ask visitors to stay on the trails with the slogan 'Don't bust the crust'.

Biological soil crustRead card
StillnessNature

Cloud forests catch water straight from passing cloud: tiny droplets collect on leaves, mosses and branches, then drip to the ground, adding a significant share of the forest's water.

Scientists call this fog drip or horizontal precipitation, because the water arrives sideways on the wind rather than falling as rain. Epiphytes, plants such as mosses, ferns and orchids that grow on other plants instead of in soil, are especially good at it: their tangled surfaces multiply the area that catches droplets. In some cloud forests, fog supplies a significant share of the water that reaches the ground in the dry season, when rain is scarce. Monteverde in Costa Rica is one of the best-studied examples, and research published there in 1999 linked warming seas to clouds forming higher up the mountains, leaving less fog in the forest. Clearing the trees removes this water catcher along with the forest.

Cloud forestRead card
Next card in the archiveArgo is a fleet of nearly 4,000 robotic floats that drift through the world's oceans, sinking to about 2,000 metres and rising again to measure the water's temperature and saltiness. At the surface each float sends its data by satellite, free for anyone to use.Read next →