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Our Planet Reviewed - Expedition Papua New-guinea :: Rubriques

Our Planet Reviewed - Expedition Papua New-guinea

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Our planet reviewed

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Biodiversity, a quite young concept

 

The first naturalist expeditions with the aim of scientifically describing the living world date back to the middle of the 18th century. Almost two hundred and fifty years later, in the mid-1970ies, biologists thought that they had identified half of the inventory of animal and vegetal species populating the planet. They dreamt, though optimistically so, of reaching the goal and of compiling an exhaustive catalogue of the living world within a reasonable time – a hope which was extinguished by the 1980ies... The development of new methods of sample-taking of little fauna finally led to a sudden re-evaluation of the forecasts and to the creation of a new word in 1986 following the first American forum on biological diversity: biodiversity: diversity of all the forms of living. Schematically, biodiversity is studies at three levels: ecosystems, the species of which these ecosystems consist and finally the characteristic genes of each species.. A term which has spread around the world although the concept it describes is still hard to define. According to Edward O. Wilson whose works have to be counted among the first to mention the word biodiversity, the term refers to the diversity of any forms of living, a variety which can schematically be studied on three levels: ecosystems, the species of which these ecosystems consist and finally the characteristic genes of each species.  
Today, while 1.8 million species have been described, it is estimated that there are still 10 or maybe even up to 30 million yet to be discovered. And it maybe even more than that. However, the clock is ticking as a major biological crisis makes itself known: the sixth extinction is already happening. In contrast to the five ones before, this one is not result of natural disasters. It is the result of the actions of one single species which at times does not live up to its name: homo sapiens, “the sapient human”.

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Racing against the clock with a handicap

 

The Millenium Ecosystem AssessmentThe Millennium Ecosystem Assessment assessed the consequences of ecosystem change for human well-being. From 2001 to 2005, the MA involved the work of more than 1,360 experts worldwide. Their findings provide a state-of-the-art scientific appraisal of the condition and trends in the world’s ecosystems and the services they provide, as well as the scientific basis for action to conserve and use them sustainably., a report which was published in 2005, shows that the human being has changed his environment more in the past 50 years than at any other point throughout his history. The consequence of this is a loss of biodiversity which leads to a degradation of the numerous services rendered by the ecosystems: provision of food (fishing, agriculture...), of fresh water, pollination, regulation of the climate etc. These tendencies are about to become more intense in the course of the 21st century which will see a further increase in the risk of poverty and starvation for a large part of the worlds population which will then in turn be obliged to increase pressure on their environment to survive which will then again in turn aggravate the loss of biodiversity.

How to break out of this vicious circle? There is no simple answer to this but it would certainly be a starting point to better get to know and understand the ecosystems surrounding us in order to preserve them. This is a titanic task which becomes even more complicated because of the emergency and the “taxonomic handicap”. Behind this expression which has been coined by the members of the Convention on Biological Diversity, facts of life are hidden: the most important and most threatened biodiversity is found in poor countries which neither pocesses  the financial means nor the infrastructure to study them and which thus suffer a deficit of knowledge in order to preserve it. For historical, economic and biological reasons, the ecosystems of the richer countries are better known. However, although they benefit from more favourable conditions, they also have to face an important taxonomic handicap: the lack of access to information, the lack of human and financial resources as well as a loss of expertise due to the ageing of the population of specialists...

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Unexpected expansion

 

Despite this difficult situation, naturalists continue to describe new species with an average rate of about 16,000 per year. While the inventory of groups such as birds or big mammals are more or less complete (new specimen are only rarely discovered), this is not the case with the very small marine or terrestrial species: molluscs, insects... The latter alone already represent a total of more than 8 million species of which only 1million have been described until today. And if one goes down several steps on the scale of size down to the dimensions of micro-organisms (viruses, bacteria, unicellular eucaryotes), the figures become even more vertiginous. Some authors however still think that the majority of the terrestrial biomass could be constituted of the micro-organisms of the ground while others call viruses « the most profuse entity of the planet». These results which are still being discussed among experts however confirm that the 1.8 million species described already only represent a small fractional part of all living species. And in this, it has not even been taken into account that there are many more ecosystems which have hardly been examined as they are difficult access or have only been recently discovered such as hydrothermal sources: Zones with major under water volcanic activity which develops at the level of oceanic ridges in depths of between 500 and 4,000 m. Their discovery at the end of the 1970ies turned the world of biology upside down: as a virtual oasis of life at the bottom of the oceans, it accommodates a rich biodiversity which is based on primary production which is no longer ensured by photosynthetic organisms taking their energy from the sun as it is on land (plants) but by chemosynthetic bacteria which take their energy from hydrogen sulphide ejected by hydrothermal sources., cold seepsCold seeps which were discovered in the middle of the 1980ies on certain continental margins correspond to natural emergence of gas and hydrocarbon exuded by sediments. As it is the case with hydrothermal sources, chemosynthetic bacteria are the basis of these ecosystems which accommodate a fauna one cannot find anywhere else on such a limited surface., ocean deeps Deeps are those zones of the oceans located in a depth of between 4,000 and 6,000 metres. They cover 307 million square kilometres, i.e. two thirds of the surface of the globe. Because of the cold, the obscurity and the very high pressures present there, they have long been considered as a desert. However, it is known that they are actually rich in original species.or canopies: vegetal region formed by the highest branches and foliage of the upper part of the trees of a forest. This region is in direct contact with the free atmosphere and light and is particularly rich in terms of biodiversity in the case of tropical forests....

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Make choices and change of scale

 

In general, considering the current rhythm of the description of biodiversity, between 250 and 1,000 years would be required in order to achieve a complete inventory. In view of this finding and given the rampant rhythm of today’s destruction of biodiversity, contemporary naturalists had to accept the evidence: it is impossible to wait for the completion of the inventory until protective measures are taken. Since it will not be possible to save all the organisms with the currently available means, choices have to be made. But what shall be preserved? The 200 eco-regions of the world of the World Wildlife Fund, the 218 Endemic Birds Areas of Birdlife International or the 34 hotspots of Conservation International? Each conservation NGO in fact has its own idea of what should be prioritised with regard to the zones to be protected which vary according to the criteria of evaluation. Luckily, these regions all share certain characteristics (elevated level of biodiversity, high number of endemic species etc.) and sometimes, their borders overlap.