At least 70% of Earth’s species still unknown
March 20, 2013
By Karina Toledo
Agência FAPESP – Although human knowledge of the planet’s biodiversity is still quite fragmented, an estimated 1,750,000 different living species have been described, including microorganisms, plants and animals. This may be an impressive number for the uninformed, but the most optimistic hypotheses say this number represents a mere 30% of the life on Earth.
“It is estimated that there are still another 12 million species awaiting discovery,” said Thomas Lewinsohn, professor in the Animal Biology Department at the Universidade Estadual de Campinas (Unicamp) during the presentation that kicked off the 2013 Conference Series organized by the BIOTA-FAPESP program, aimed at improving scientific education.
However, how can the extent of our lack of knowledge on biodiversity be evaluated? “To accomplish this, we extrapolate based on the most-studied groups of organisms to evaluate the least-studied. Regions or nations where the biota is well known guide evaluation of the less well-known places. We arrive at these estimates via the Rule of Three,” he explained.
Lewinsohn said that more recent techniques use sophisticated statistical formulas based on rates of discovery and description of new species. The values are adjusted according to the strength of existing work, or, in other words, the number of taxonomists currently working.
“However, the most important thing to say is that there is no consensus. Estimates can be as high as over 100 million unknown species. We really don’t know how big a number it is, and this is alarming,” he said.
In his estimation, Lewinsohn believes it would take 2,000 years to describe all the species thought to exist in Brazil. “It would take about this long to describe all the species in the world. However, we don’t have that much time,” he said.
Some recent techniques in molecular taxonomy, like DNA barcoding, can help speed up the work, as they allow for identification of organisms through analysis of their genetic material. In this method, different DNA chains differentiate species, while in traditional taxonomy classification is based on the morphology of living beings—a much more cumbersome task.
“Can it be done? Yes. But how much would it cost?” pondered Lewinsohn. An article recently published in the journal Science noted that between US$ 500 million and US$ 1 billion would have to be spent every year for 50 years to describe most of the species on the planet.
Again, the numbers may alarm those not familiar with the problem, but Lewinsohn says that the total amount is equal to the money spent on military arms in only 5 days. “In 2011 alone, US$ 1.7 trillion was spent on arms. Things need to be put into perspective,” he argued.
Nevertheless, many of these unknown species could disappear from the planet before mankind has the time and money to study them. According to data presented by USP Biosciences Institute Professor Jean Paul Metzger, over 50% of the face of the planet has been transformed by human activity.
There are many consequences of this change in landscape, and Metzger addressed two of them during the day’s second presentation: loss of habitat and fragmentation.
“They are different concepts that are oftentimes confused with one another. Fragmentation is the subdivision of a habitat and may not happen when damage happens along the edges of a forest. Construction of a roadway, for example, creates isolated fragments within the habitat,” he explained.
In Metzger’s opinion, fragmentation is the largest threat to biodiversity because it changes the balance between species’ natural extinction processes and colonization. The smaller and more isolated the fragment is, the higher the extinction rate and the lower the colonization rate.
“Each species has a minimum amount of habitat that it needs to survive and reproduce. We still don’t exactly understand these thresholds to extinction,” he alerted.
Metzger believes that this threshold can vary according to landscape configuration, meaning the more fragmented the habitat, the greater the risk of extinction for the species that live there. For example, he cited the remaining areas of Atlantic Rain Forest in São Paulo State, where 95% of the fragments are less than 100 hectares in size.
“It is estimated that when 90% of habitat is lost, 50% of the endemic species are lost. What remains of the Atlantic Rain Forest is some 16% of the original forest. One would expect mass extinction, but our records show few cases. Either our theory is wrong, or we aren’t detecting the extinctions underway because we don’t even know the species exist,” affirmed Metzger.
There is a complicating factor, however: the latent period between changes in the landscape structure and the changes in community structure. Although species with short life cycles can disappear quickly, those with longer life cycles can respond to habitat loss on a scale of a hundred years or more.
“An extinction debt is created. Even if changes to landscape are interrupted, some species are still destined to disappear over time,” said Metzger.
However, the good news is that landscapes also regenerate themselves naturally, and there is a recuperation credit in addition to the extinction debt. The latency period represents, therefore, an opportunity for conservation.
“We have evidence today that it’s not worthwhile to restore in just any location. Priority areas for restoration must be defined that will optimize connectivity and facilitate the biological flow between fragments,” stated Metzger.
Reaping the fruits
Throughout the 13 years of BIOTA-FAPESP’s existence, one of the main concerns of its researchers has been to define priority conservation and recuperation areas within the State of São Paulo.
The results of their studies have been used by the State Environmental Secretariat as the basis for public policy, as related by Carlos Alfredo Joly, BIOTA coordinator and professor at the Unicamp Biology Institute, during the day’s third and final presentation.
“Today, at least 20 legal instruments, including laws, decrees and resolutions, include references to BIOTA-FAPESP results,” said Joly.
The coordinator said that R$ 8 million were invested every year between 1999 and 2009, helping to finance 94 research projects and resulting in 700 articles published in 181 periodicals including Nature and Science.
The program’s team also published 16 books and 2 atlases, described over 2,000 new species, produced and catalogued information on 12,000 species and made 35 biological collections from the state available online.
“Since FAPESP funding for the program was renewed in 2009, education has become our priority in strategic planning. The objective of this series of conferences is to increase communication with groups beyond the scientific community, especially teachers and students,” said Joly.
The lecture series will continue as follows: March 21, “The Pampa Biome”; April 18, “The Pantanal Biome”; May 16, “The Cerrado Biome”; June 20, “The Caatinga Biome”; August 22, “The Atlantic Rainforest Biome”; September 19, “The Amazon Biome”; October 24, “Marine and Coastal Environments”; and to finish the series, on November 21, the topic will be “Biodiversity in Anthropic Environments—Urban and Rural”.Republish
Agência FAPESP licenses news reports under Creative Commons license CC-BY-NC-ND so that they can be republished free of charge and in a straightforward manner by other digital media or by print media. The name of the author or reporter (when applied) must be cited, as must the source (Agência FAPESP). Using the button HTML below ensures compliance with the rules described in Agência FAPESP’s Digital Content Republication Policy.