Author: Dr Leila Battison
Over the last few decades, it has become clear that direct human actions and anthropogenic climate change pose a major threat to the Earth’s biodiversity. The widespread occupation and modification of terrestrial habitats by the arguably pestilent human species has driven animals and plants from their natural homes, isolating and constricting populations. Meanwhile, hunting, fishing, and poaching activities have hacked away at the numbers of select species, chosen for their delicious meat, good sport, or mythical medicinal qualities.
In an attempt to understand the severity of this particular environmental crisis, the International Union for Conservation of Nature (IUCN) first compiled ‘The Red List’ in 1964, using a number of quantitative criteria to classify the level of threat posed to animal, plant, and fungal species. This list has been used to garner public interest, prioritize conservation measures, and support governmental policies with respect to national and international biodiversity. Today, the concept of an ‘endangered species’ is widely toted in the media, and the poster children of conservation efforts, such as the Giant Panda and the Black Rhino, are household names.
Now, 52 years since its inception, and with swelling datasets and generational trends, we are beginning to see the effects of Red List-guided conservation efforts. Has the classification and identification of species at risk been a positive influence on populations and communities, or have the statistical analyses simply written these animals’ fates in indelible ink? Does the list fairly encompass all species at risk, or are some being left to die out in the dark? What does the future hold for our global biodiversity?
A drop in the ocean?
Within the list, a species can be classified within one of five groups, indicating increasing risk to extinction: Least Concern, Near Threatened, Vulnerable, Endangered, and Critically Endangered. In order to qualify within one of these groups, populations must meet one of a number of criteria, designed to capture the multitudinous ways in which a species can be threatened. These include a reduction in total population size over a generational timescale, a limited geographic range, or a significant probability of extinction on the basis of specialist quantitative analysis (1). Although the Red List is administered by the IUCN, the classifications are made on the basis of vast quantities of collected data, and the combined efforts of many scientists over many years. Some debate remains about the validity of certain metrics under specific conditions, such as the accuracy of the often-used quantitative population viability analysis with small datasets, or the use of ‘extent of occurrence’ to define geographic ranges with outlier population groups. However, the provision of a variety of possible criteria increases the probability that populations are properly classified, despite highly variable population structures, generation lengths, and habitats.
To date, over 76,000 species of animals, plants, and fungi have been assessed, with more than 22,000 found to be at some risk of extinction. But this is just a drop in the ocean of Earth’s total biodiversity – with an estimated 8.74 million species, not including prokaryotes, we’ve investigated less than 1% (2).
A Bleak Prospect
But a one-off assessment isn’t enough. As with all ecological systems, population changes are dynamic, and depend on human actions as well as the health of the overall ecosystem. As such, repeated assessments are just as critical, to judge the effects of changes over varied timescales. A Red List report published in 2011 provided such a review, offering a bleak perspective on the state of our biodiversity. They found that, despite conservation efforts, 25% of mammals surveyed are still at some risk of extinction (3). Damning numbers indeed.
One of the most widely publicized recipients of conservation efforts today is the Rhino. This species is a prime example of the conflict between conservation and continuing exploitation. Although the total numbers of Black Rhinos have increased worldwide, with more than 5000 across Africa, certain subspecies remain at great risk from illegal poaching and hunting for their horns, and they remain critically endangered (4). With the Western Black Rhino having been declared extinct in the wild, and the Javan Rhino extinct in Vietnam in 2011, conservation efforts have reached all-new extremes. For instance, a Tanzanian game reserve has become famous for protecting 15 White Rhinos by enclosing an area of 21 square miles with eight-foot high electric fences, defended by 24-hour armed guards (5). But the resources are not available for every rhino to be protected in this way. In this case, conservation rulings and enhanced publicity from Red List assessments have not been enough to protect these much sought-after herbivores from the actions of rogue individuals.
Recovering Biodiversity
The prospects are not all bleak, however, and there have been numerous cases of successful population recovery. The 2011 Red List report brought good news for Przewalski’s Horse, the only true wild horse, native to central Asia, which had been declared extinct in the wild in 1996. After a very successful captive breeding programme, the population of these wild horses now totals more than 300 in their native Mongolian habitat, with a naturally reproducing herd in the unmanaged wildlife refuge of the Chernobyl Exclusion zone. The IUCN has now reclassified this species, raising it from extinct in the wild to simply endangered (6).
A similar success story surrounds the Giant Panda, the literal poster child of the World Wide Fund for Nature (WWF). These large, sedentary herbivores have a very limited diet and a very ponderous attitude to mating, and have suffered a slow decline as a result of habitat loss and population fragmentation. However, since the introduction of strict conservation measures, including a 20-year prison sentence for killing a giant panda, their declining trend has taken a U-turn. Today, there are over 1850 individuals in the wild, in 35 isolated populations; this represents an increase of 16.8% over the last 10 years (7).
Most recently, the happy reclassification of the West Indian Manatee has made the news. The Endangered Species Act (ESA) first classified the tubby marine mammals as endangered over 50 years ago, as overhunting and collisions with dense boat traffic had brought them to the brink of extinction. In 1991, aerial surveys counted just 1267 in the waters around Florida. In response to this, the gentle seacows were protected under the Marine Mammal Protection Act, which aims to improve the response rate to strandings and administers permits in order to manage culling operations. This year, a new study counted more than 6300 around Florida, in addition to roughly 13,000 individuals in the Caribbean and along the coast of Venezuela and Brazil. Thus, the endangered status of the West Indian Manatee is now under review, with a proposal to downlist the species to ‘threatened’(8).
Preserving genetic diversity and trophic richness within individual habitats is key to maintaining biodiversity over longer timescales. These species are not cute, they are not cruelly hunted, and they may not even have common names, but they form the base of the precarious house of cards of Earth’s biotic diversity.
Why do we care?
So it would seem that the methodical assessment of species under the Red List is of considerable value in helping to understand population changes, and in successfully enacting conservation measures. The results of such measures seem to vary between individual species and situations, but the accurate study of species distributions and their threats can only help in slowing or reversing biodiversity decline.
However, some fundamental issues still surround our approach to conserving Earth’s biodiversity. It is painfully clear that the species receiving the most interest under the Red List classifications are large mammals found within some of the planet’s more accessible habitats. This is no accident – larger mammals are more easily found, tracked, and identified, making them ideal targets for population studies. They also receive plenty of publicity, thanks to the ‘cute’ public image perpetuated by conservation groups. Yet these so-called apex consumers are arguably the least important from the perspective of Earth’s ecosystem health. Instead, the relatively non-descript plants, fungi, and plankton upon which the planet’s food webs rely can, and should, be considered more worthy of conservation attention. Preserving genetic diversity and trophic richness within individual habitats is key to maintaining biodiversity over longer timescales. These species are not cute, they are not cruelly hunted, and they may not even have common names, but they form the base of the precarious house of cards of Earth’s biotic diversity. If just one of these fundamental species goes the way of the dodo, passenger pigeon, or Tasmanian tiger, we will be faced with a much greater problem than the lamentable loss of a single beautiful creature. Let’s hope that some of the target 160,000 species to be assessed in the next few years (9) will be these critical foundation taxa.
Thus, in an attempt to answer the questions posed, the classification and identification of species at risk has generally been a positive influence on populations and communities. However, the list does not fairly encompass all species at risk, some are being left to die out in the dark. Sadly, the future still looks bleak for our global biodiversity.
Sources:
1) http://www.iucnredlist.org/technical-documents/categories-and-criteria/2001-categories-criteria
2) http://www.iucnredlist.org/about/overview
3) http://www.bbc.co.uk/news/science-environment-15663982
4) http://www.worldwildlife.org/species/black-rhino
5) http://www.telegraph.co.uk/news/earth/wildlife/9525512/Rhinos-under-24-hour-armed-guard.html
6)http://blogs.scientificamerican.com/thoughtful-animal/10-things-you-didne28099t-know-about-przewalskie28099s-horses/
7) http://www.worldwildlife.org/species/giant-panda
8) http://www.fws.gov/news/ShowNews.cfm?_ID=35428
9) http://www.iucnredlist.org/about/overview