Debate: Which is the world's most invaluable species?

Plankton, bats, primates, fungi and bees - which species would have the greatest impact on our planet if it were lost? Five experts set out their case public debate in London next Thursday

Jessica Aldred, guardian.co.uk 14 Nov 08;

Fungi

'It keeps the trees alive, recycles waste and helps us'
Professor Lynne Boddy of the Cardiff School of Biosciences

Fungi have a bad reputation, usually being thought of as poisoners, rotters of food and homes, causes of plant disease and human infections (eg athlete's foot). In fact, very few fungi cause a nuisance. Moreover, without fungi humans could not exist. Most terrestrial plants obtain their nutrients and water from soil through fungi associated with their roots. Furthermore, fungi are the main garbage disposal agents and nutrient recyclers of the natural world. They are hugely important as food for soil animals and in producing human food, eg Quorn, cheese, chocolate and soft drinks. Fungi produce many "wonder drugs" including penicillin and statins to control cholesterol.

Within this vast kingdom of organisms that is so crucial to our very existence, it is hard to single out just one species. However, my choice would be Amanita muscaria, the fly agaric. This fungus forms mycorrhizas with the roots of forest trees, providing them with water, mineral nutrients, protection from pathogens and some pollutants. It also recycles dead organic matter. It is used as a food source by some animals, and produces powerful chemicals that may turn out to yield novel pharmaceuticals.

Bees
'Bees are irreplaceable. Their loss will be catastrophic'
Dr George McGavin of the Oxford University Museum of Natural History
Honeybee

The partnership between flowering plants and pollinating insects, especially bees, is one of the most widespread and significant symbiotic interactions on Earth. This 100m-year-old collaboration has spawned a rich diversity of species and promoted the rise to dominance of humans.

Now the need to feed our burgeoning population, coupled with the agricultural means to that end – a plethora of pesticides, the unabated loss of natural habitat and the translocation of alien species and diseases - are driving wild and managed bee populations into a very steep decline. Seventy percent of the crop species eaten by humans depend wholly or partly on pollination and recent estimates put the economic value of insect pollination at over £121 billion ($192bn) - representing at least 10% of the value of the world's agricultural production.

Bees are irreplaceable and the debate about what might happen if they disappeared is no longer academic. We have set in motion processes that may lead to the extinction of the planet's most important pollinators along with countless other species that depend on them. Not only will the world be a much less colourful place, it will also be poorer in every other way imaginable. The effects will be nothing short of catastrophic.

Plankton
'Plankton are the base of the whole food web'
Professor David Thomas of the School of Ocean Sciences, University of Bangor
Earthwatch debate: Plankton

Plankton is a collective term for a myriad of bacteria, viruses, plant-like microbes and small animals that drift at the mercy of the winds and the ocean currents and wind. They are the base of the whole food web that lives in just about any body of water you care to imagine: from your bird bath in the garden up to the vast oceans that cover most of the planet.

Temperature extremes hold no bounds and plankton survive being encased in ice in our Arctic and Antarctic oceans and can survive near boiling waters in hot springs. Not only that, but plankton cells can be carried large distance in aerosols in the wind, and some people even believe they can survive in space. They not only fuel aquatic ecosystems, but some release gases that can influence cloud formation and therefore global climate.

But apart from how vital the plankton are to running planet Earth, they are simply beautiful to look at. Plankton have been an inspiration to artists and designers ever since the first microscopes were invented, and plankton inspired design can be found on a whole range of scales from buildings to wheel hubs.

Bats
'Bats provide a number of these essential services'
Dr Kate Jones of the Zoological Society of London
Earthwatch debate: Bats

We are in the midst of a mass extinction of this planet's life brought about by humans monopolising global resources and changing global climate patterns. Many species provide essential services eg, disease control, clean water, pollination and insect regulation, and we are now faced with an agony of choice. Given finite amounts of conservation dollars, which species can we not do without? I present the case for bats.

Bats provide a number of these essential services; for example without bats many commercially important crops such as bananas, mangoes, dates and tequila would fail. Insects consumed by bats translate to millions of dollars saved on pesticides. Bats are also indicators of general ecosystem health and monitoring their populations provides us with early warning systems of irreversible damage.

Bats also have many irreplaceable traits, they are the only mammals to use powered flight, can hunt and navigate in the pitch darkness using only sonic echoes, provide the imagery of Dracula and the flying creatures of Halloween. Perhaps some of us couldn't cope with fewer fungi in our lives, green goo in our rivers, bees to sting and annoy, and primates that one day might rise to overthrow us, but to me a world without bats is unthinkable.

Primates
'Primate habitats provide ecosystem services we all depend upon'
Ian Redmond, chief consultant of the great apes survival project
Earthwatch debate: Gorilla

Monkeys, apes and lemurs must be saved, not just because they share so much DNA with humans (although blood is thicker than water, so this convinces many people), not because they are fascinating research subjects (though clearly they are), not because they are intelligent social mammals who have every right to exist (though arguably they do); not even because primate-watching can form the basis of multimillion-pound tourist industries, creating jobs and lifting rural communities out of poverty.

Any one of these would be reason enough to fight for the survival of our zoological next-of-kin, but I would argue that their ecological role as keystone species in tropical and sub-tropical forests is more important.

Primate habitats provide ecosystem services we all depend upon – especially absorbing carbon while releasing oxygen through photosynthesis and pumping water into the atmosphere through evapo-transpiration, which drives global rainfall patterns. What most people fail to recognise, however, is that primates sow the trees of tomorrow by dispersing seeds in their dung.

If we want these forests to be a permanent carbon store, a source of clean water and to regulate our climate in future, we had better not kill the gardeners of the forest today.

• The Earthwatch debate Irreplaceable - the world's most invaluable species, takes place from 7-9pm at the Royal Geographical Society in London on Thursday November 20. Free to current Earthwatch supporters, but by ticket only. For all others, a donation will be requested on the door. Doors open 6pm (cash bar). The debate will be followed by an optional buffet supper with wine, £25. For tickets and information please call +44 (0)1865 318856 or email events@earthwatch.org.uk

The animals and plants we cannot live without
From the Amazon rainforests to the frozen ice fields of the arctic, animals, plants and insects are disappearing at alarming rates from pollution, habitat loss, climate change and hunting.

Richard Gray, The Telegraph 15 Nov 08;

Nearly 17,000 species are now considered to be threatened with extinction and 869 species are classed as extinct or extinct in the wild on the International Union for Conservation of Nature's Red List. In the last year alone 183 species became more endangered.

Now, in the face of the growing threat posed by environmental changes around the globe, five leading scientists are to argue whether there is a single type of plant or animal which the planet really cannot afford to lose.

The debate, titled Irreplaceable – The World's Most Invaluable Species, will see five experts present the case for the world's most important animals and plants from a shortlist of five: primates, bats, bees, fungi and plankton.

Primates, which are among the most threatened of animals, are likely to win hearts due to their cuddly exterior while those with a sweet tooth for honey will doubtless sympathise with the bees, which are suffering near catastrophic declines.

Fungi are among the most abundant organisms on the planet and include amongst their numbers the Earth's biggest living organism, a giant fungus known as Armillaria ostoyae which stretches for 2,384 acres in Oregon's Blue Mountains.

Bats are the biggest family of mammals and the only one that can fly, but are threatened by habitat loss and persecution by humans.

Plankton provides food for some of the smallest and biggest animals on the planet, including the Blue Whale.

Here we examine the contenders in detail and asks if we can afford to lose any of them at all.

PRIMATES

Number of different species: 394

Weight: 1 ounce to 440 pounds

Strength in numbers: 400,000 great apes, around a billion other primates

Threats: 114 species are threatened with extinction. Bushmeat hunters and habitat loss are the main threats

PRIMATES are our closest cousins. By studying them and watching their behaviour, humans have been able to gain a remarkable insight into our own beginnings and how our complex cultures have developed.

Primates share more than 90 per cent of our DNA. For Chimpanzees, our closest relatives, the similarities in our genetic code has surprised even the experts.

They are also of great economic importance in many countries – in Rwanda and Uganda the Mountain gorillas are now the number one source of foreign currency income through tourism.

Ian Redmond, chairman of Ape Alliance, an international coalition of organisations and individuals working for the conservation and welfare of apes, said: "Primates are a keystone species in tropical rainforests. They are major dispersers of seeds as they eat fruits and then dispense the seeds in little packets of fertiliser around the forest.

"We need to protect primates today in order to have forests tomorrow that can absorb carbon dioxide from the atmosphere and prevent the erosion of soil."

BATS

Size: 2 grams (0.07 ounces) to 1.5kg (3 pounds)

Number of different species: 1,100

Strength in numbers: billions

Threats: 1 in five species are threatened from habitat loss and persecution

Legends of Dracula and tales of vampire bats have done little to enhance these creatures' reputations. Only one species is the notorious blood sucker, while most feed on insects and fruits.

Bats are the only mammal capable of flying and are so highly evolved to be capable of pinpointing a single insect flying in the pitch black and plucking it out of the air using echo location.

For this reason they are a major predator of insects and play a key role in controlling insect numbers. They are also the most abundant mammal on the planet – one in five mammals is a bat.

"Bats have an extraordinary diversity, which makes them an essential part of the ecosystem," said Dr Kate Jones, a bat expert from the Zoological Society of London. "They are also a key indicator species that can provide information on the health of an ecosystem.

"They occupy a wide range of habitats from urban areas to caves and forests.

"Most crucially, bats are major agents of pollination and seed dispersal. Without them many crops would fail because they play such an essential part of the ecosystem."

BEES

Size: Around half an inch

Number of different species: 20,000 known species of bee

Strength in numbers: Billions of individuals – a single honey bee hive can contain 40,000 bees

Threats: Disease and climate change have seen populations plummet by up to 80%

Without bees, humans would starve. These industrious little insects are the world's greatest pollinators, carrying a dusting of pollen from flower to flower as they gather nectar for their hives. Millions of years of evolution has seen many plants become almost entirely reliant upon bees to help them breed.

Crops such as almonds, peaches, avocados and apricots are totally reliant upon bee pollination.

The total worldwide economic value of pollination has been estimated to be around £130 billion a year, and that is without the honey and wax that bees also produce.

Bee numbers have, however, fallen by up to 80% in some parts of the world due to disease, climate change and pesticide use. The situation has grown so critical that beekeepers are warning there will be no British honey left in the shops by Christmas.

George McGavin, an honorary research associate at Oxford University's Museum of Natural History, said: "The planet could go on functioning quite happily without any large animals such as primates.

"We rely upon bees for just about every vegetable, flower and fruit around. They are a crucial terrestrial group and we would face mass starvation without them."

FUNGI

Size: a single cell to 2,300 acres

Number of different species: Up to 1.5 million

Strength in numbers: millions of billions

Threats: Probably the least threatened group and the cause of threat to many other species in the form of disease

FUNGI are a much maligned group of species. They include pests that can kill gardeners' plants, diseases that are responsible for ailments such as athletes foot and moulds that leave unsightly stains in our houses.

But without fungi we would not have gardens, houses or even feet at all. It was fungi that first allowed plants to move out of the oceans and on to land by establishing a symbiotic relationship that still exists today.

It is a fungi, known as mycorrhiza, that allows plants to obtain nutrients and water from the soil. Rather than directly sucking these essential building blocks of life into its roots, plants have to rely upon the fungi to gather it for them from the surrounding soil.

"It was fungi that allowed plants to move onto land around 600 million years ago," explained Professor Lynn Boddy, a mycologist at the Cardiff School of Biosciences. "Without fungi we would still be living in the ocean."

The other main role that fungi perform is as nature's recyclers. They clean up remains of dead plants and animals by decomposing them and returning the nutrients they hold back to the environment to be used again.

"They are involved in the production of many foods too," added Professor Boddy. "Mushrooms are fungi, but also bread, beer, cheese and chocolate all rely upon fungi to be produced. Many drugs such as penicillin come from fungi too."

PLANKTON

Size: 10 micrometres (0.0004 inches) to 1 millimetre (0.04 inches)

Number of different species: 50,000 in the light zone of the ocean alone

Strength in numbers: Billions of trillions

Threats: Pesticides and pollution can damage plankton blooms

It is hard to feel too attached to plankton. A drifting soup of microscopic algae, creatures and bacteria, they are not even one group of species but bridge entire taxonomic kingdoms. Plankton is essentially anything living in water that is too small to swim against the current, including krill and algae.

But despite its small size, blooms of plankton are visible from space and can sustain billions of marine creatures. The plant-like organisms in plankton, known as phytoplankton, are found close to the surface of the water where there is sufficient light to allow photosynthesis.

"Half of the world's oxygen is produced by these organisms," explained Professor David Thomas, from the school of ocean sciences at the University of Bangor. "If you took that away you would lose the basis of life on the globe. There simply wouldn't be enough oxygen to support life."

The bacteria also provide a vital role by breaking down organic material in the water and recycling dead organisms. The zooplankton, which encompass a wide range of little organisms from single-cell protozoa to creatures such as jellyfish, krill and copepods, provide the basic link in the ocean food chain.

Professor Thomas said: "If you go back far enough in time, life started in the plankton, so we owe it a remarkable debt."

The Irreplaceable debate is being organised by environmental research charity Earthwatch and is being held at the Royal Geographical Society in London on Thursday 20 November. Entry is free and doors open at 6pm.

For tickets and information please call 01865 318856 or email events@earthwatch.org.uk

And here are a few species we may be happy to do without

Wasps

Capable of injecting venom from the end of their sting even after they have died, it is a popular question faced by entomologists - what are wasps actually good for?

Rats

They carry plague and live in the sewers. Even Sir David Attenborough, the wildlife presenter, does not like them.

Feral Pigeons

Known as the rats of the sky, they are considered pests in most city centres around Britain

Woodlice

These scuttling crustaceans thrive in the warm damp corners of houses and are reputed to be a good substitute for prawns in seafood sauces

Stinging Nettles

The bane of all schoolboys who have ever been forced to wear short trousers. Although nettle soup is a known delicacy.