A project to count all the arthropods in the San Lorenzo forest of Panama could help to give a much more accurate estimate of the number of species on Earth. The project discovered that for every plant species there were 20 species of arthropods, for every species of birds there were 83 species of arthropods and for every species of mammal there were 312 species of arthropods.
Those ratios appeared to be constant across different areas of a tropical forest. If other ecosystems have similar ratios then it could make it easier to estimate the total number of animal species on the planet.
We can think of it in terms of being on an aeroplane. The Earth is the plane and the species are the bolts holding the machine together. Some of these bolts are more important than others. We can lose some of the bolts, but if too many go missing the plane is going to crash.
“After nearly ten years of work, we have determined that Panama’s San Lorenzo forest is home to 25,000 arthropods. This is the very key to resolving the question of how many species there are in the world,” states Frode Ødegaard, a Senior Scientist at the Norwegian Institute for Nature Research (NINA), and a main member of the international research team.
The team of 102 international researchers spent nearly 10 years in the San Lorenzo forest and searched the forest from the soil to the heights of the canopy for every species of arthropod in the area. Over 130,000 specimens were collected from over 6,000 species of arthropod.
A large portion of all species discovered in the forest were found in a rather small area – a fortuitous development for the researchers.
“What this means, basically, is that we can determine the diversity of species within a tropical forest by examining smaller areas and then extrapolating the findings,” Dr Ødegaard explains.
One of the things the researchers discovered was that you could estimate the number of species of arthropods by counting the diversity of plant species in an area. The finding supported previous studies and theories that biodiversity was underpinned by plant diversity.
The researchers discovered that for every species of plant found, there would be 20 species of arthropod. Similarly, there are 83 species of arthropods per species of bird and 312 species of arthropods per species of mammal.
Understanding the diversity of arthropods is important as they make up an estimated 70% of species on the planet. Despite being so wide spread little is currently known about how many species there actually are. With most of the species of arthropods being found in tropical forests being able to make much more accurate estimates of species number is essential.
Now that the San Lorenzo forest has been surveyed Frode Ødegaard and his research team has moved on to a rain forest at Papua, New Guinea to compare the findings of rain forests on two different continents.
“This study has shown that the time has come to think big,” Frode Ødegaard says. “Only by means of large-scale collaboration projects will we be able to gain insight into existential questions of this type. Previous examples include the collaborative efforts to map the human genome and understand the nucleus of the atom at CERN.“
So why is it important that we understand how many species there are on the planet? Ødegaard uses the analogy of an airplane. “We can think of it in terms of being on an aeroplane. The Earth is the plane and the species are the bolts holding the machine together. Some of these bolts are more important than others. We can lose some of the bolts, but if too many go missing the plane is going to crash.”