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Contact: Karin Hannukainen
University of Helsinki

Scientists climb through and fly over a rain forest to count its bugs

A new study uses comprehensive sampling and species identification to uncover the full species richness of a complete rain forest

To collect bugs from the tree crowns, the researchers used what they call a "canopy raft" - a deformed rubber boat moved with the help of a helicopter.
Photo by Stéphane Bechet

Most animals on earth are arthropods living in tropical forests. Yet, counting them is hard work – so hard that no one has previously been able to count the bug species of even a single forest. Now more than one hundred scientists have teamed up to sort this out by crawling, climbing and sifting through a tropical forest of 60 km2. Their findings are described in the journal Science.

The group was led by Yves Basset from the Smithsonian Tropical Research Institute. Based on the bugs collected from twelve intensively-studied sites in a rainforest in Panama, the researchers suggest that that the full forest will hide around 25,000 arthropod species.

“What most earlier studies have done is to focus on just a few groups of bugs, and use just a few methods for collecting them. For example, scientists would beat the branches of trees and bushes, and count all the beetles raining down. What we did was to go all out and collect all sorts of creepy-crawlies from the soil to the tree roof in as many ways as we could”, says researcher Tomas Roslin of the University of Helsinki, Finland.

To do this, the field team first sampled the rainforest canopy from a crane, from inflatable platforms, from balloons and by climbing ropes. They also crawled along the forest floor to sift soil and trap and bait arthropods. However, the biggest job was still to come: As the researchers had found nearly 130,000 arthropods, it took them eight years to sort them and identify them.

Altogether, the researchers found more than 6,000 species in their material from the twelve sites they explored. From this, they then calculated that the full forest will hide some 25,000 arthropod species.

“In this forest, scientists have already counted the birds, mammals and plants, but the bugs are poorly known. Now that we know that there are 25,000 arthropod, it means that for every species of plant in this forest, you will find approximately 20 species of bugs, for every bird, you will find 83 bug species, and for every mammal, you will find 312. So – if we want to save species the species on Earth for the future, we should start thinking about how best to save the bugs.”

To the researcher´s surprise, the number of bug species closely mirrored the species richness of plants. The more plant species a site had, the more bugs the scientists found. And when you went from one to two to three sites, the number of new bugs and plants increased in much the same manner.

“This is very good news”, says Tomas, “because it means that we can save a good deal of the bug species by protecting areas with plenty of plants. After all, the number of plant species are much easier to count than are the tiniest creepy-crawlies.”

Yves emphasizes that what made this work possible was that so many researchers worked together. “Altogether, we were 102 researchers from 21 countries working together on this. To solve big questions, we researchers really need to help each other.”


Read the full press release on EurekAlert here: http://www.eurekalert.org/pub_releases/2012-12/stri-mbf120612.php

Y. Basset et al. Arthropod Diversity in a Tropical Forest. Science 338, 1481-1484

For more information, please contact the lead author of the article, Dr Yves Basset, Smithsonian Tropical Research Institute, Panama (bassety@si.edu, ph +507 2128233) and/or Dr Tomas Roslin, University of Helsinki, tomas.roslin@helsinki.fi