Whales in Hot Water? The Impact of a Changing Climate on Whales, Dolphins and Porpoises: A Call For Action Page: 4
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:)bservations since 1961 shw
that the average temperature of t,
global ocean has increased to
depths of at least 3000 m and that
the ocean has been absorbing mc
than 80 % of the " added "
climate system.
IPCC.
change some cetacean species may respond by shifting
their distributions to remain within optimal habitat.
However, in some cases such range shifts will not be
possible. For example, the northern Indian Ocean is fringed
by land, limiting the ability of species to move northwards
into cooler habitat as waters warm. Similarly the distribution
of the endangered vaquita (Phocoena sinus) is limited to the
warm waters at the northern end of the Gulf of California.
River dolphins such as the Ganges river dolphin (Platanista
gangetica) and the boto (Inia geoffrensis) may also be
particularly vulnerable to temperature changes within their
strictly limited habitats.vii,viii Other examples are less
immediately obvious but still significant. Off northwest
Scotland, the common dolphin (Delphinus delphis), a warm
water species, is apparently increasing its range, while the
white-beaked dolphin (Lagenorhynchus albirostris), a cold
water species, is seemingly reducing its range, and fewer
sightings and strandings of the latter are being reported.
White-beaked dolphins are generally found in cold water less
than 200m deep off northwest Europe.
Their ability to respond to climate change by locating new
suitable habitat may be limited because there is a lack of
suitable shelf waters further north. Temperature rise thereforeTable 1: Species range, status and potential effects of climate
change on cetacean species listed as threatened by IUCN
(either vulnerable, endangered, or critically endangered.)Species
nameBalaena
qlacialis
Megaptera
novaeangliae
Balaenoptera
borealis
Balaenoptera
physalus
Balaenoptera
musculus
Physeter
macrocephallus
Platanista
gangetica
Inia
geoffrensis
Lipotes
vexillifer
Delphinapterus
leucas
Cephalorhynchus
hectori
Phocoena
phocoena
Phocoena
sinusCommon
name
Northern
riqht whale
Humpback
whale
Sei whale
Fin whaleSpecies range
NAtlantic & Pacific:
subpolar to tropical
Worldwide: cold temperate/
polar to tropical
Worldwide:
cold temperate to tropical
Worldwide: polar to tropicalBlue whale Worldwide: polar to tropical
Sperm whale Worldwide: polar to tropicalGanges river
dolphin
Boto
Baiji
Beluga or
white whale
Hector's
dolphin
Harbour
porpoise
VaquitaIndia, Nepal, Bhutan and Bangladesh:
freshwater only
Peru, Ecuador, Brazil, Bolivia, Venezuela,
Colombia: freshwater only
China: freshwater only
Circumpolar in arctic seas:
arctic to cold temperate
New Zealand: coastal waters,
cold to warm temperate
N Pacific and NAtlantic:
subpolar to cold temperate
Gulf of California: subtropicalIUCN Potential
status effects
of climate
change on
species
EN (D) ?
VA(A) ?
EN(A) ?
EN(A) ?
EN(A) ?
VU(A) ?
EN(A)
VU(A)
CR (ACD)
VU(A) ,
EN (AC) I
VU(A) ?
CR(C) ,Source: Learmonth et al. 2006. Ibid.
Note: indicates a possible decrease in range, and ? indicates that the effects on range are unknown.
is likely to have serious implications for white-beaked
dolphins, and may lead to a decline in abundance or
fragmentation of the species' distribution. ix
Climate change will also have indirect impacts on cetaceans,
such as a probable increase in susceptibility to disease and
contaminants and changes in the availability and abundance
of food resources, particularly for whales which have
specialised feeding habitats. The prey species of manyFigure 1: Climate change and cetaceans; a simplified representation of major impacts.
Climate change and cetaceans;
a simplified representation of major impactse
Se ee i
E l'asoiaee
-
Htels
Othr u ma ipats
/
74
Freshening
of seawater (ice
melt, increased
rainwater)11 WQ lw,
swr4
CEAEN
FIH Q I
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Elliott, Wendy & Simmonds, Mark. Whales in Hot Water? The Impact of a Changing Climate on Whales, Dolphins and Porpoises: A Call For Action, text, May 2007; Gland Switzerland. (https://digital.library.unt.edu/ark:/67531/metadc226703/m1/4/?q=%22ecological%20impacts%22: accessed May 4, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; .