Some data seem difficult to estimate because counting seems impossible. But Australian researchers risked making such an assessment. They were able to estimate the number of birds on Earth.
Huge amount of data
“For the fields of ecology, evolutionary biology, and conservation, estimates of the abundance of organisms are crucial. However, quantifying abundance is difficult and time consuming.“, emphasizes a new study published on May 25, 2021 in the journal PNAS. This is where participatory science comes in: it allows for the rapid collection of large amounts of data anywhere on the planet. The authors of this study compiled more than a billion bird sightings reported on the eBird website by no less than 600,000 people between 2010 and 2019. Biologists have also developed an algorithm whose calculations took into account the detective ‘species, ie the probability that a person noticed bird and reported it on the site. The species becomes more visible, for example, if the birds fly in groups, if they are colorful or of good size. The goal of the scientists: to estimate the number of birds on Earth.
They took into account about 92% of all species, or 9,700. The remaining 8% are too rare to be detected or data related to them are not available because they are “sensitive” species that may be victims of human trafficking. Birds that do not count should in any case only subtly change the global estimate obtained from biologists.
Domestic sparrows are the most numerous
The study reveals that the Earth has more than 50 billion birds. By comparison, the human population is close to eight billion. Four bird species reach one billion specimens: the house sparrow (1.6 billion), the common starling (1.3 billion), the ringed gull (1.2 billion), and the barn swallow (1.1 billion). Unfortunately, this evolutionary success is little shared. “It is a rare species and relatively few common species“, note Australian researchers. Thus, about 12% of the species studied in this study have less than 5,000 birds. Kiwis (3,000 birds) and Mesitornithidae (154,000 birds) are the two least overgrown orders in the world, while nursery (28 billion) more numerous “.Quantifying species abundance is a crucial first step in conservation, remark in Statement Dr. Corey Callaghan who piloted the study. By correctly counting the existing one, we find out which species could be vulnerable“.
What about mistakes?
Researchers recognize that despite their precautions, there remains a degree of uncertainty when working with such a large data set. So, “it is possible that participants preferentially observe rarer species, potentially inflating their abundance“Or, conversely, the species may be so rare that it harms it, and the power of its assessment falters.”Our results, although approximate in some areas, represent the best available data currently available for many species.“However, Professor Shinichi Nakagawa, a statistician and co – author of the study, is exacerbating the situation. As new data is collected, the estimate will be refined.