Tragedy of the commons? Don't be so melodramatic...

The 'tragedy of the commons' is a fairly well known ecological dilemma, which arises from the fact that people will exploit a shared resource to exhaustion before they will deplete a resource that they own themselves. This concept was first described by the ecologist Garrett Hardin in 1968 and is often used to help plan for sustainable development in an area.

The basic principle underlying the tragedy of the commons is this: an individual who uses their own resources for a service gets the benefit of that resource, but at a cost - they have had to use up resources that they personally own and consequently, cannot use them again. However, an individual who uses a shared resource for a service still gets that all of the benefits that this entails, but they are not using up their own resources. Thus, the individual gets all of the benefits from a service, but at no personal cost. So using common resources seems like a good idea, right? And yes, it is for an individual at their own personal level. The problem is however, that many individuals will have worked out that they can use the resource at no cost to themselves and as such, the common ground will be over used and will be exploited until it is completely depleted and becomes useless. This fact led Hardin to coin the phenomenon of the 'tragedy of the commons': multiple individuals that are acting rationally and in their own personal best interests (as they usually are) will ultimately deplete a shared resource, even when it's clear that this is not always in the best interests for the resource for them to do so.

Note how most of the sheep in this photo have red paint sprayed onto them with one (left), instead having yellow paint. This tactic is often used by farmers to mark their own livestock when grazing them on shared resources so that they can identify their own animals later.

The classic example for the tragedy of the commons and the one used by Hardin to first describe it, is medieval land tenure by European herders. A group of herders all have their own land on which to graze their animals, which by using, they will benefit by having their livestock fed and healthy. However, by feeding their animals off their land they are using up their own grass and without grass, the land's soil is washed away and it may eventually become useless. Knowing this, herders take their livestock to the village or town common instead - land which none of them own and allow their livestock to graze here. Therefore, their animals are still fed but they are not degrading the quality of their own land so that the herders, on a personal level, are in a 'win-win' situation. But, although this is good for a single herder, there is a major problem with this as you've no doubt realised. The problem is that while a single herder may have for example, 10 sheep, which would take a very long time to use up and deplete a field, multiple herders are using the field at the same time. Hence, if 10 herders use it who all have 10 sheep, then 100 sheep are all feeding off the same field - meaning that its resources will quickly be depleted. This rapidly degrades the quality of the common, meaning that soon it will not be able to support livestock and, with poor muddy ground, cannot really be used for recreation either (the purpose for which it was made available to everyone).

This photograph shows the heavy land use of grazing cows. It is unlikely that a single farmer owns so may cows so this is probably a shared resource - a resource which is clearly being overexploited. Even though this overgrazing will rapidly degrade the quality of the land, it allows farmers to feed their cattle at no personal cost to themselves so that they will be inclined to use it until it has been exhausted.

The tragedy of the commons can be applied to all common resources and modern-day examples include overfishing in the world's oceans and industrial logging in the world's rainforests: such resources are either not privately owned or are too big for that ownership to be enforced effectively, so that they are overexploited by multiple groups and as a result, are being rapidly degraded.

The tragedy of the commons is frequently used in arguments that support sustainable development programmes, allowing such programmes to satisfy both conservation and economic entities by encompassing economic growth and environmental protection. Furthermore, it is regularly used as a warning against the implementation of policies that restrict the use of private property or espouse the expansion of public land - factors that may drive individuals into exploiting shared resources! The tragedy of the commons is also used to argue for the privatisation of resources in order to protect them and although desirable, this is often impractical. How, for example, can you privatise the ozone layer or honeybees? To complicate things even further some areas, such as the Amazon Rainforest, are just too big - even it was completely privately owned it is unlikely that it could be protected in its entirety and therefore it is unlikely that illegal logging could be effectively prevented!

Therefore the tragedy of the commons is an issue of logic, where any rationally acting individual will first exploit a shared resource before using their own because this is in their best interests. This means that it is very hard to prevent and in order to combat it, policies must be put into place to control overexploitation and where possible, encourage individuals to use their own resources preferentially to shared ones.

Extinct bee is re-introduced into the UK

The short-haired bumblebee has been extinct in the United Kingdom since 1988, where its numbers declined as the result of the dramatic increase in farming that followed World War II. This extensive farming was needed to fuel Britain's rapid population growth and sadly, about 97% of the bees wildflower-rich grasslands have now been lost. 

The short-haired bumblebee, Bombus subterraneus. Bees vision is at the ultraviolet end of the electromagnetic spectrum so the insects see blues and purples very prominently, as well as light that our eyes cannot see. As a result, they seem to prefer blue and purple flowers to those that are red or yellow.

However, the loss of their habitat hasn't phased conservationists in the Royal Society for the Protection of Birds (RSPB) in their reserve at Dungeness, Kent (one of the larger counties in the UK). The team have spent the last three years planting as many many wildflowers as possible and have created lush meadows that are already benefiting other species of endangered bee that are still endemic in the UK, such as the shrill carder bee, and the RSPB now thinks that they are ready for the short-haired bumblebee to make its return.

"There will be a really good chance that it [the short-haired bumblebee] will establish, it will  become self sustainable and spread." Nikki Gammons from the Short-haired Bumblebee Project.

The generosity of the Swedish government has made the bee's return possible, who have given scientists permission to go and collect up to 100 new queens from their countryside. The short-haired bee is still common in Sweden and removing a small number of queens such as this shouldn't have an impact on their populations there. Once in the UK, 20 - 30% of the queens are expected to survive their hibernation over their first winter here (which is very high odds for the survival rates of an introduced species) and the colonies that they form are expected to be able to survive fairly well in RSPB Dungeness, persisting there long-term.

Many local farmers are also involved in the project, which also been funded by Natural England and the Bumblebee Conservation Trust (in addition to that of the RSPB), who are planning to leave the edges of their fields untouched. These wild strips, or 'corridors', will contain many of the flowers that the bees need to survive and will help the short-haired bumblebee to spread across its ancient endemic ranges throughout southern England.

Want to help the bees?

Although the re-introduction of the short-haired bee into the UK will hopefully be a success, it doesn't change the fact that bee numbers are crashing worldwide. There are various reasons for this - some are due to man and some are not; but regardless, their loss will have profound implications to us. Bees are estimated to be involved in the production of around a third of all human food by pollinating our crops and represent US$40 billion in terms of the services that they provide to the human agricultural industry - in the UK alone, bees contribute more than £400 million a year to our economy by pollinating crops and medicinal plants!

The production and use of highly toxic neonicotinoid pesticides is one of the major contributors to the demise of bees, a fact that AVAAZ is trying to remedy. By signing their petition you can support AVAAZ when they confront Bayer (one of the major producers of the pesticides) and try to get the company to stop their production. Please consider spending a few seconds to sign this petition - bees are crucial organisms for global ecosystems and need our help!

Death of the giant eagle

700 years ago the largest bird of prey and one of the largest aerial predators that has ever lived hunted in the skies over New Zealand's South Island - Harpagornis moorei, more commonly known as Haast's Eagle. The bird, weighing up to 15kg (which is very heavy for a bird as they have hollow bones), had a wingspan of 3m and was the top predator in its ecosystem - hunting the moa (Dinornis novaezealandiae), a 12 foot high flightless bird that weighed in at almost 230kg!

Haast's Eagle was a specialist predator and almost exclusively hunted moa, soaring at high altitude before dropping out of the sky at speeds that are estimated to be as fast as 50mph, striking the flightless bird with enormous force! Wounds on the bones of moa suggest that once the eagle was within striking distance of the hapless bird, it grabbed its prey's pelvis with one talon and the crushed the back of its neck with the other. It is believed that the eagle then landed on top of the moa and, if it was still alive, quickly finished it off using its very large and razor sharp beak. Unlike many modern-day predators that have to compete with scavengers for their kill, the isolated island habitat of New Zealand did not have such animals, which enabled H. moorei to have consumed all of its kill by itself, returning to the carcass for up to a week after it was killed! The fact that the eagle could utilise the vast majority of its kill is believed to be one of the reasons that the species evolved to be so large.

An artists impression of Haast's Eagle hunting moa. Despite the eagle's very large size, which is pushing the boundaries of body mass for powered flight, it had a very short wing span. This is believed to be an adaptation for hunting over the scrubland and forests of New Zealand because it allowed them to hunt in dense vegetation.

The other reason that the eagle grew to such an impressive size is believed to be due to a phenomenon called 'island gigantism', which is likely the main driving force behind the evolution of its growth. Island gigantism is a relatively common biological trait where species that live on isolated islands with no contact to the mainlands grow to be unusually large. This may seem strange, but makes sense biologically as these isolated islands often develop their own unique ecosystems due to the fact that the more abundant species that live on mainlands cannot get across to them. As a consequence of this, there are relatively few species inhabiting the island so that such animals are under little competition for resources. Thus, animals on isolated islands are able to fuel large body growth and often evolve to be unusually large. The isolated nature of such islands also means that many of the species that live there have evolved independently from those on the continent so that many of the organisms found on cut-off islands are unique, being found nowhere else. A good example of such novel species are the strange species of marsupials that are found in Australia, which broke away from Africa 184 million years ago. These marsupials have therefore, evolved independently from continental species for a very long period of time.

Growing to lengths of 3 metres the Komodo dragon, Varanus komodensis, is the world's largest species of lizard and the world's biggest poisonous animal. The lizard is found spread across certain islands in Indonesia and is an excellent example of island gigantism, with its large size being attributed to a lack of competition over prey as there are no other species that fill its niche on the islands.

Bizarrely, phylogenetic analysis of the DNA of H. moorei has found that the eagle is not related to other large species of predatory eagle as you might expect, but is instead most closely related to the Little Eagle, Hieraaetus morphnoides. This rather small bird of prey is about the same size as a Peregrine Falcon, weighing a mere 815g! Although it is slightly odd that the ancestor of the Little Eagle remained at such a diminutive size while one of its cousins became one of the most massive aerial predators ever, it in fact supports the idea that island gigantism fuelled the evolution of the colossal size of H. moorei: a small number of the ancestors of the two eagles were trapped in New Zealand after it separated from Antarctica between 130 and 85 million years ago, whilst others remained over the larger continent. Those over the continent had greater competition for resources so could not fuel the growth needed to reach such huge sizes and consequently, evolved into the Little Eagle. Those trapped in New Zealand however, had an abundance of food and evolved into the giant Haast's Eagle.

This shows the foot of H. moorei (left) compared with that of a Little Eagle (right). It has been calculated that the massive eagle's talons could have pierced and crushed bone up to 6mm thick under 50mm of skin and flesh!

Although the large size of the eagle is very impressive it also, rather unfortunately, led to its downfall. Unsurprisingly its extinction was due to the arrival of man to New Zealand, as one of the main characteristics of human invasion into a new environment is the extinction of its endemic megafauna - such large animals provide excellent sources of food and are typically very vulnerable to the alterations that humans make to their habitat. In this case however, humans did not hunt and kill Haast's Eagle directly; instead killing it by wiping out the moa, leaving the eagle with nothing to eat. Obviously, a 12 foot flightless bird was easy pickings for the early Maori settlers (who came from Hawaii) and they exploited the bird, hunting it mercilessly. This over-hunting would have wiped the moa out eventually, but the problem was made even worse because moa eggs were also considered as a delicacy and were raided from the birds nests. This was a huge factor in the moa's rapid extinction because they only laid a few eggs every year; meaning that there were nowhere near enough young moa to replace the adults that were being killed by humans for meat!

Once the moa became extinct it was only a matter of time before Haast's Eagle followed it into the abyss,  mainly because it had evolved to a specialist predator that hunted moa almost exclusively. However even if H. moorei knew how to have hunted the other animals resident to New Zealand, none of them were large enough to have fed it for long so the birds would have eventually starved to death anyway. Although such an end to a species is not uncommon and has happened many times in the past, it is still a sad and rather undignified end for such a majestic species and Haast's Eagles have not soared above the far-flung islands of New Zealand for over 600 years...

Help save the bees!

Hi all,

This isn't a proper post as I won't be writing any new articles now until early June (after my exams have finished), but I wanted to draw your attention to a petition by AVAAZ that is trying to get Bayer shareholders to vote to stop the company from producing very harmful neonicotinoid pesticides that are killing large numbers of bees globally and are significantly contributing to their catastrophic decline.

As you may or may not know, bees are crucial organisms for pollinating many species of plants and flowers and without their services very few of the planet's ecosystems will be able to survive. Bees are known to help in the production of around a third of all human food and represent an estimated US$40 billion in terms of the services that they provide to the agricultural industry. Simply put, they are irreplaceable. 

Although these pesticides aren't the only factor contributing to the decline of bees, they are a major 'player' and stopping their use is under our direct control. Please spend a few seconds to sign this petition, which is in the best interests of everyone worldwide and can have a direct result as Bayer are one of the major manufacturers of these harmful chemicals.

Thanks, 

David

May hiatus

Hi all!

It's a busy period for me at the moment - I've got lots of deadlines rolling up and have exams running throughout May (thankfully my last exams ever!). This means that unfortunately, I don't have time to keep publishing posts on this blog so I will be taking a break through May in order to focus on my work. I hope you have enjoyed reading my posts thus far and I will resume regular posting after I have finished my course, so be sure to check back early in June!

David