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Aantal soorten in de wereld
Toby Young (2019) schrijft het volgende:
"..........the number of species in the world is unknown. The most reliable estimate is 8.7 million (with a margin of error of plus or minus 1.3 million), but even the compilers of that stat acknowledge that 86 per cent of all species on land and 91 per cent of those in the seas have yet to be discovered, described and catalogued. Ik vraag me dan wel af hoe je dan kunt weten ddat die "onontdekte" soorten er wel zijn.


UN’s Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES).

2019: press release put out by the IPBES and a ‘summary’ of the report ‘for policymakers’. The press release states: ‘The report finds that around one million animal and plant species are now threatened with extinction, many within decades.’ It gives no source for this beyond the as-yet-unpublished report, but the summary makes it clear that it’s partly based on data from the International Union for Conservation of Nature (IUCN) Red List of Threatened Species (see below).

Munch-de schreeuw
Edward Munch: De Schreeuw
(klik voor vergroting)
 

Het lijkt er sterk op dat het IPBES het IPCC naar de kroon gaat steken met alarmistische boodschappen:

In hun persbericht wordt gesproken van "One million species at risk of imminent extinction".

‘It says "The Earth’s ecosystems are being destroyed by the relentless pursuit of economic growth."

(bron: Toby Young (2019)

Threatened or vulnerable ? (Bedreigd of kwetsbaar ?)
IPBES’s claim that ‘around 25 per cent of species… are threatened’? That seems a little pessimistic, given that the number of mammals to have become extinct in the past 500 years or so is around 1.4 per cent and only one bird has met the same fate in Europe since 1852. Not bad when you consider how much economic growth there’s been in the past 167 years.

So what does ‘threatened’ mean?
The IPBES is using the IUCN’s definition, which is ‘at high risk of extinction in the wild’. Rather implausibly, the IUCN includes species in this category that it designates as ‘vulnerable’, which it defines as facing a ‘probability of extinction in the wild’ of ‘at least 10 per cent within 100 years’. About half the species the IPBES includes in its 25 per cent figure are in this ‘vulnerable’ category.


International Union for Conservation of Nature (IUCN) Red List of Threatened Species.

The IUCN’s Red List website says that ‘more than 27,000’ species ‘are threatened with extinction (bron:Toby Young (2019). Toch al weer veel minder dan 1 miljoen van het IPBES !


There is very low confidence that observed species extinctions can be attributed to recent climate warming,
Paul Homewood, May 17, 2019

Another claim apparently made by the BBC’s "Costing the Earth" (red.: een BBC-radio-programma) was that “hundreds of species” were going extinct every day. 

Whatever the numbers, according to the IPCC there is little evidence that the rate of extinction has been increasing over the last several decades, or that recent extinctions have been due to global warming:

" ........across all taxa there is only low confidence that rates of species extinctions have increased over the last several decades (birds: Szabo et al., 2012; but see Kiesecker, 2011, for amphibians). Most extinctions over the last several centuries have been attributed to habitat loss, overexploitation, pollution, or invasive species, and these are the most important current drivers of extinctions (millennium Ecosystem Assessment, 2005b; Hofmann and Todgham, 2010; Cahill et al., 2013). Of the more than 800 global extinctions documented by the International Union of Conservation of Nature (IUCN), only 20 have been tenuously linked to recent climate change (Cahill et al., 2013; see also Hoffmanet al., 2010; Hof et al., 2011b). Overall, there is very low confidence that observed species extinctions can be attributed to recent climate warming, owing to the very low fraction of global extinctions that have been ascribed to climate change and tenuous nature of most attributions".
Source: https://www.ipcc.ch/report/ar5/wg2/


Websites:

Zie ook onze webpagina "Het grote uitsterven van 251 miljoen kaar geleden".

Literatuur:
- Ridley, Matt, Biodiversity threat won’t be tackled by alarmist biologist hype and dismantling capitalism, Reaction, May 7th 2019.
Ook verschenen op Ridley's blog "rationaloptimist.com", 8 mei 2019: A COUNSEL OF DESPAIR ABOUT THE LOSS OF BIODIVERSITY IS THE WRONG APPROACH

- Young, Toby, UN's Extinction warning doesn't add up, The Spectator, May 11th 2019. (kijk hier indien de link verbroken blijkt)


Zie ook onze webpagina over biodiversiteit


U bent hier: inhoudsopgave - aarde - Milankovitch cycli
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