Monday, August 17, 2015
Hawai'i's depleted natural treasure chest: oh, what we've lost
There were many jewels in Hawai`i’s natural treasure chest,
and today, the rarest of these are the land snails.
The Hawaiian archipelago's natural legacy was a splendid array—forest birds in all the colors of
the rainbow, flashing reef fishes found nowhere else on the planet, and the
stunning silver and crimson, gold and purple hues of the flowers.
In that array, the land snails may not stand out, although there were once hundreds of species. Today, they are recognized for
their singular rarity.
(Image: One of the last remaining amastrid land snail species on
O'ahu, Laminella sanguinea, in the
Waianae Mountains. Credit: Kenneth A. Hayes, University of Hawai’i)
There were once 325 species of Amastridae that were unique to
these islands. Today, only 15 can be found.. An extinction rate of more than 95
percent.
This tally was published in the journal "Conservation Biology"
by researchers from the University of Hawai`i’s Pacific Biosciences Research Center, Bishop
Museum, and national and international teams. It is entitled “Extinction in a
hyperdiverse endemic Hawaiian land snail family and implications for the
underestimation of invertebrate extinction."
Of the 325, only 33 are officially listed as extinct on the International
Union for Conservation of Nature (IUCN) Red List. But that’s because the
paperwork can’t keep up with the rate of extinction.
“Of the 325 Amastridae species, 43 were originally described
as fossil or subfossil and were assumed to be extinct. Of the remaining 282, we
evaluated 88 as extinct and 15 as extant and determined that 179 species had
insufficient evidence of extinction (though most are probably extinct),” the
authors wrote.
When scientists write about extinction crises, they’re often
mostly talking about vertebrates—the birds and mammals, fishes and reptiles.
But to miss the invertebrates is to miss
a lot.
“Invertebrates have received much less attention despite
their constituting as much as 99% of animal species richness,” the authors
write.
To assess the status of Amastridae, the researchers studied
collections in the Bishop Museum and then went into the field, looking t 481
potential snail habitats throughout the Islands.
“At many sites, we collected leaf litter and soil, which we
searched under a microscope for especially small snails. This is the most
comprehensive and temporally focused land snail survey effort ever undertaken
in the Islands,” they wrote.
They found just the 15. If you’re interested in the list,
here it is.
“These 15
species were recorded
during recent field work,
including our field work specifically targeting amastrids in the Waianae
Mountains of Oahu (Amastra cylindrica ,
Amastra micans , Amastra spirizona , Laminella sanguinea , Leptachatina
cerealis , Leptachatina crystallina , Leptachatina gracilis , Leptachatina
gummea , Leptachatina persubtilis, Leptachatina popouwelensis ), on
Kauai (Leptachatina cuneata , Leptachatina
cylindrata), on Maui (Laminella
aspera , Leptachatina nitida), and on the island of Hawaii ( Leptachatina lepida),"
What could have caused this extinction catastrophe? Not just
one cause. The authors make a list.
Humans (early Hawaiians) arrived and launched habitat
destruction. They also brought Polynesian rats, which ate some snails but weren’t as
big an issue as later introductions.
Then came Europeans with the next big wave of extinctions, caused by pigs, goats, and other species.
Polynesian rats and black rats arrived and were big predators of snails.
Massive land clearing for ranching and plantation
agriculture added to the toll, along with introduced predatory snails, and
ants, and competition from introduced non-predatory snails.
Some of the same authors also participated in another paper
that looked at extinction of poorly known life forms globally. Again, it
suggests the extinction rate in modern times is far higher than we’ve believed.
Among its points: “Mammals and birds provide the most robust
data, because the status of almost all has been assessed. Invertebrates
constitute over 99% of species diversity, but the status of only a tiny
fraction has been assessed, thereby dramatically underestimating overall levels
of extinction. Using data on terrestrial invertebrates, this study estimates
that we may already have lost 7% of the species on Earth and that the
biodiversity crisis is real.”
© Jan TenBruggencate 2015
Posted by Jan T at 7:50 AM
Labels: Agriculture, Archaeology, Birds, Botany, Conservation, Zoology
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