Note! for best printed results, set your page up with a left margin of 1.5cm (0.6") and right margin of 1.0cm (0.4")
The whole article covers about 0.35MB (30 pages), including text, drawings and photographs.
For corrections and suggestions, e-mail the author.
--Seafriends home--conservation index-- sitemap-- Rev:20010926,20021111,20021206,20040709,20070725

This graph, derived from all the known fossil finds, shows how biodiversity evolved over time. It took a very long time before life had developed a reproducing cell. Then in the Cambrian epoch, the number of species and families soared, only to level off some 450 million years ago. Three extinctions followed, the largest one at the end of the Permian, heralding the epoch of the dinosaurs. Then biodiversity took off again, suffering yet another great extinction at the end of the Cretaceous, which saw the end of the dinosaurs and the rise of mammals. The extinctions caused by humans are profound and estimated at 100-1000 times the natural rate, indeed comparable to that caused by meteorite impact (the believed cause of the extinction of the dinosaurs). But their causes are different, and entirely related to the increase and spread of the human population and its wastefulness (see also threats for more details):

• habitat destruction: humans have destroyed vast amounts of habitat for living, and for their crops, leaving little undisturbed for nature. Remaining pockets of natural ecosystems have been fragmented by surrounding farmland, roads and canals. Many of such small pockets do not work like one large area, resulting in loss of species over the long term.
• introduced species: wherever humans moved to, they brought along with them domesticated species like livestock, pets, crops, grasses and ornamental plants. They also introduced diseases, pests and weeds. These species compete with the native species, and often displace them.
• overexploitation: the hunting of food and fur species, collection of ornamental species, and persecution of annoying, threatening or competing species. The logging of native timbers and trees for firewood.
• pollution: pollution of the environment and ocean by human wastes, industrial wastes and agricultural chemicals. Some of these chemicals have been produced in high energy processes, which makes them impossible to degrade biologically. Waste of mineral resources.
• competition: competing with other species for food, like ocean fishing. Although humans do not spread out into the oceans for dwelling, they nonetheless compete with ocean wildlife for food. Likewise, the harvesting of natural forest products, competes with wildlife.

As dead as a dodo The dodo (Raphus cucullatus) is an extinct flightless bird related to the pigeon, and as large as a turkey.  It had short legs, an enormous beak, stubby wings, and a tuftlike tail with curly feathers. It laid a single egg on the ground.  European sailors, having rounded the Cape of Good Hope, were in desperate need of food, which they found in plentiful supplies on the island of Mauritius, between Madagascar and India. Dodos moved clumsily and slowly and were easy to catch. They also had a nice taste, while their copious amounts of fat made them easy to preserve. Pigs and monkeys brought to the island by Portuguese sailors during the 1500's destroyed the eggs and ate the young.  The dodo died out about 1680. The heads and feet of a few dodos are preserved in museums, but their relatives (solitaires) on Reunion and Rodrigues Islands, are known only from pictures, from accounts written by travellers, and from bones that were found on Reunion and Rodrigues islands.  The dodo and solitaires belong to the pigeon and dove order, Columbiformes.  They are in the dodo and solitaire family, Raphidae.  The Reunion solitaire is classified as Raphus solitarius, and the Rodrigues solitaire as Pezophaps solitaria. The Reunion solitaire became extinct in about 1750, and the Rodrigues solitaire about 1800. But the story of the dodo does not end here. A tree known as Calvaria major, also confined to the island of Mauritius, was a puzzle to botanists for centuries. Once quite common on the island, it had gone into decline until only 13 ancient trees, all over 300 years old, were left. Although they produced plenty and healthy-looking seeds, none ever germinated. In the mid-1970s, an American ecologist, Stanley Temple, came up with an explanation. He suggested that the tree's large fruits had formerly been eaten by the dodo, whose stone-filled gizzard exerted a powerful crushing pressure. Birds often swallow stones to make their gizzards (stomachs) work even better. To withstand this onslaught, the tree's seeds adapted a thick-walled seed coat for protection. The dodo's gizzard pounded away at this coat, making it much thinner, and perhaps cracking it a bit. When deposited by the bird, the seed could germinate. As the dodos became extinct, the seeds could no longer escape from their thick-walled armaments, and the trees slowly died out, as no replacement seedlings sprouted. Only by human intervention can this tree species now survive. (Adapted from: Linda Gamlin and Gail Vines: The evolution of life. 1986.)

The International Union for the Conservation of Nature (IUCN) has defined the following grades of endangeredness (for more detail see the NZ Red Data Book and for more authoritative detail, visit www.redlist.org:
 
 

People are obsessed with fire-fighting, courageously and with much effort saving a species from the brink of extinction, but to the grand scheme of nature, this is not important. We have already lost a huge numbers of species, and will lose a great deal more. It is therefore important to focus on those that are not in a critical state, and to provide them with the habitat and space they need. This is already costly and difficult enough.

Scientists are rushing to know precisely how many species exist on Earth, and to even register the extinct ones, but would all this effort change our actions? Would it really be beneficial to those who survive? Would it even be beneficial to us?
We know that the only acceptable and effective course of conservation consists of limiting the spread of people, limiting the population and stopping habitat destruction and fragmentation. We know what to do. Now we need to do it.

f026502: Hector's dolphins (Cephalorhynchus hectori) are endemic to New Zealand, and their numbers are estimated at around 3000, classifying this small species as endangered. In various places, fishing methods have been restricted to prevent them from drowning in set nets but the dolphin's main enemy is degradation of the sea by runoff from the land. These dolphins live strictly coastally, which brings them into conflict with people and also in highly degraded waters.

f210411: New Zealand's yellow-eyed penguin visits the land for nesting, where it is threatened by habitat destruction and predation. In this sheltered bay of the Flea Bay (Pohatu) marine reserve near Christchurch, it is protected by the vigilance of its caretakers.

How many species? Scientists differ enormously over the estimated number of species on the planet. They are furthermore hampered by the fact that no integrated library of species exists, although a beginning has just been made. They also suffer from the low regard for taxonomy, the description and classification of organisms, due to it being considered a low level of science. However, they may be wrong on this, because biodiversity is the total stock of genetic information of the planet, a huge library of life.

Another problem is that we simply haven't looked in all places. In the diagram on right, the number of known fish species is shown for New Zealand. As soon as the Extended Economic Zone was ratified, and scientists started to systematically sample the area, a large number of new species, never before seen by human eyes, was discovered. They now discover two new fish species every month, and scores of other unknown organisms, as long as they keep looking.

Here follow two recent developments in the effort to put meaning to the concept of biodiversity and extinction.
 

Extinction is frightening for a number of reasons:

• It is permanent: it cannot be undone. There is no way back.
• It is insidious (sneaky): humans are not good at noticing the absence of things. If half the birds died overnight, without leaving a trace, perhaps nobody would notice. Only by careful observation and recording, can the gradual decline or absence of organisms be noticed.  Humans are also inept in noticing slow change, and extinctions happen slowly. All presently endangered species will be extinct tomorrow, unless exceptional care is applied.
• It could cause a domino effect: by disturbing the balance in the environment, other species become endangered too, but later. Many rare species live in close relationship with another species. If one goes, the other goes too.
• The mathematics of scarcity predict massive increases: the world's habitats have already been changed by 50%, resulting in a loss of 12% of all species. But this loss increases very rapidly since the remaining area decreases very rapidly. The next 25% loss of habitat will lose as many species again.

Prehistoric colonisation of islands in the Pacific and Indian Oceans by humans and their commensals (rats, dogs and pigs) may have led to the extinction of as many as a quarter of the world's bird species. Since 1600, as many as 484 animal and 654 plant species are recorded as having gone extinct. This is almost certainly an underestimate, especially for tropical regions.  Because of the world-wide loss of natural habitats that has already taken place, tens of thousands of species are already committed to extinction. It is not possible to take preventive action to save all of them. The graph shows how an almost constant extinction rate suddenly escalated for island communities, as populations there reached their limits. A wave of extinctions for continent communities followed later, but abated due to the green revolution, which requires a smaller area for cultivation. (UNEP GBA)

Human use of the biosphere is represented by the thick black line. It starts at the bottom left with zero human population, and it ends at the top right with all space occupied by humans. How fast we climb up this black line, depends on how much habitat we change and how many wastes we produce, thus our dependence on both our cropland and ecoservices. It is affected by population size and economic activity.

In order to survive, humans need ecoservices, to recycle their wastes (see chapter above). Consider the area under the black curve, our use and the area above it, that available to nature. Then it is clear that the unused part will be declining as people use more. In the era of plenty (before now), the services exceeded our needs, giving us 100% service (red line). We observe the blue skies, the clean air, enough drinking water, and our wastes not causing major problems.

However, at the halfway point, this is going to change rapidly according to the formula (1-x) / x, describing the amount of nature remaining, divided by the population, which amounts to personal ecosystems services (red curve). As one can see, it will suddenly start plummeting down, causing serious problems perhaps as early as the year 2020, problems which are not yet apparent today.

As the area used by people increases, it correspondingly leaves less for nature. From what we know about the relationship between area size and number of species, extinctions can be expected to follow the green curve. It starts at the top left corner, where zero humans are leaving 100% of the planet for other species, and it ends at the bottom right where 100% of human use leaves no room for other species. At the 50% point, mid-way, 0.25 x 50%= 12.5% of species are threatened with extinction by the amount of habitat destroyed by humans. They are on the way out. Up to 25% loss of all species can be expected by 2030. After that, more still. This in turn reduces the quality of nature's services. In all, the near future may herald some sudden and 'unexpected' nasty changes.

The World Watch Institute (www.worldwatch.org) reports that in the year 2000, some 1.2 billion people worldwide struggle to survive on $1 day or less. 1.2 billion people lack access to safe drinking water and 2.9 billion have inadequate access to sanitation. About 150 million children are malnourished, and more than 10 million children under 5 will die in 2001 alone.
The question arises, how many will be in famine in 2020 or in 2040? An intial reaction would be that the proportion would be the same, so for a doubling in population, one would expect twice as many in dire need (2.4 billion). One may expect that biotechnology comes to the rescue, just in time to save all. But the fact is that GE does not have a usable technology today. It took the green revolution 50 years to where it is now. Most of the increase in food came from bringing new land under culture. But both the water supply and land have come to their limits, and are now even reducing in quantity. Knowing that famine is never spread equitably, but only to those who can not afford the minimum, it is more likely that famine will more than double, it is even possible that it could swell the underfed to 6 billion (five-fold increase). This is also part of the logic of scarcity.

It appears that Man is administering to himself the same prescription for extinction as he did to other species: habitat destruction and introduced species (himself). Note in this respect, that not a word was said about our presently perceived threats, of the end of fossil fuel, global warming, sea levels rising and so on. It is likely that our main problems will arrive from somewhere else, like habitat destruction (nature + human habitat), and that they have not shown up yet. However, once they do show, the problems will arrive thick and fast, according to the logic presented here. But a word of caution is in place.

First of all, humans are not spread evenly over the planet, so some places will notice the effect of human habitat destruction much sooner and more severe than others. Secondly, where humans have destroyed the habitat for other species, they have often planted a habitat capable of providing some human ecosystems services, such as timber forests, rubber plantations and so on. Since most of our ecosystem services are provided by bacteria, which are more resilient than higher organisms, our waste treatment may follow a different logic. Finally, the oceans are very large and mainly unchanged. They will continue providing ecosystems services, even though the land, rivers and coastal seas may have suffered severely. Also remember that some countries are further up the slope than others.

On an optimistic note, it follows that whatever we can do now to reduce the harmful side effects of our actions, will help to slow down our climb up the black ramp, with its unavoidable consequences.
 
 

Reader please note that the mathematics of scarcity is not mainstream science, but consists of my own ideas. Discussion welcome.

The way the number of species depends on area, has important consequences for the size of protected areas. The smaller these are, the fewer species will be protected. In the example above, 35 species were found in 300m2, but 20 were found in every 10m2. A reserve for the most common 20 at 10,000 individuals each, would require 10,000x10m2 or 10ha. To protect the next 15 species, would need a reserve of 10,000x300= 300ha.

It is often argued that 10 reserves of 30ha would achieve the same, but there are a number of reasons why this is not so:

• boundary effect: reserves are usually surrounded by changed habitat, like rich forest remnants by poor grassland. In the boundary of the two, one finds species encroaching on each others patch, resulting in displacement. In case the outside is the same habitat but exploited, one finds species diffusing from the rich to the poor diversity areas, only to be caught or hunted. The effective protected area thus becomes substantially smaller. Often mainland 'island' reserves are shaped like ribbons, following state boundaries or infrastructure (roads, trains, canals), which makes the boundary effect very large. Large predators will wander out of the reserve and annoy humans. Notice that real islands do not have boundary effects: no influx of predators, no outflow of wildlife, no influx of pests and weeds. Because of their long period of isolation, a large percentage of unique endemic species have evolved.
• fragmentation: although the area is the same, the mainland islands are not interconnected, and species cannot migrate. Of the rarer species, some are found on one island and not enough on another. On land, males and females must be brought in direct contact with each other, so they must be able to physically find one another. In some areas, too many predators are found, against none in others. Plants often rely on the pollen from other plants, or the birds and insect that pollinate. These must all be sufficiently present in each island reserve. In all, small reserves end up with much poorer biodiversity than anticipated.
• clumping: in nature, species are not distributed evenly, but occur in patches, groves, leks (breeding territory) and so on. Some of the island reserves will therefore have different compositions, resulting in different communities.
• Allee effect: Warder Allee observed that some species find it very difficult to breed successfully once the population falls below a certain number or density. Some species need to congregate in thousands, before the level of security by numbers, or physical excitement is reached to start reproducing. Most animals are not sexually active all year round, but need to be brought up to that state. It may explain the sudden demise of the passenger pigeon.
• ice ages and global warming: temperature shifts require (poikilotherm=cold-bodied) species to migrate north or south. Forests do this slowly by seed. Because island reserves are surrounded by alien habitats, this movement is not possible. In large reserves, however, a much larger degree of movement is possible.

The relationship between evapotranspiration and plant productivity above (eco21.gif) also has important consequences for the size of protected areas, since all life ultimately depends on the amount of green food available. A mountain puma in a cold climate would need much more territory than a lion in a savannah grassland, which needs more than a jaguar in a tropical rainforest. Cold climate reserves may need to be 10x larger than warm climate reserves. Likewise dry climate reserves must be larger than wet climate reserves. Protected areas must attempt to protect both the total functionality and resilience (sustainability) of the ecosystem, which is severely compromised by a small size.

May R M, 1975: Patterns of species abundance and diversity, in Ecology of Species and Communities pp81-20. (eds M Cody, J M Diamond) Harvard Univ Press.