Sorry for the lack of posts in the past 1.5 week, I was
caught up finishing two important essay deadlines during reading week :’( But
good news is, we will be focusing on a rather new aspect of the topic today – Responses
from Keystone Predators. For those who are new, just to recap, my chosen topic
focuses broadly on how global warming has recently affected a range of
biodiversity, and the observed responses they have taken to adapt to these
rapid changes in climate. Previously, I have focused on observed shifts in
vegetation (eg. Arctic Greening) and biomes worldwide, as well as looking at how
North Sea fishes are migrating northwards to a whole new level! So if you’re
interested, feel free to browse through and comment!
Anyways, back to the point on today’s post.
As mentioned previously, average temperatures worldwide have climbed about 0.6 degrees in the past century, and a further increase in 1.4- 5.8 degrees is expected over the 21st century. For
certain regions in America, this means major shifts in snowfall patterns and
length of winter that might potentially cause tremendous observed changes in species
interaction. Lets take a deeper look into how the keystone predator – Gray Wolves
- have recently responded to changes in snowfall patterns in 2 regions, and the
direct/indirect cascading effects it has had on other trophic levels (or so
called the ‘trophic cascade’).
Gray Wolf as Important Climate Change Buffers
The first case study
originates from Yellowstone National Park, where winters have extended for more than a week between 1948-2005. Luckily for scavenger species there, Gray wolves
close to extinction at one point have returned to play a vital position in
easing the consequences of shorter winter on the local food chain.
So you ask, how do they act as
climate change buffers and help other local species to cope with climate change?
Well, basically they provide a reliable supply of carricon (decaying flesh of
dead animals) for scavengers throughout the whole winter season, regardless of
whether it's a mild or severe winter.
Let me explain this more
clearly. During severe winters, more elk
dies, providing important food sources for a wide range of scavengers in the
Yellowstone National Park, such as ravens (Corvus corax), magpies (Picapica), grizzly bears (Ursus arctos) …and many more for their survival and reproduction. Due to climate change,
however, warmer (milder) winters locally cause an increase in survival rate of elks, resulting in food shortages
for scavengers when other food resources are scarce during certain times of the
season. Luckily with the help of Gray wolves tend to leave their leftovers
behind and elks are frequently killed despite of the duration of severity of
the winter season.
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| Elk and other species in Yellowstone National Park, USA |
Thereby, it is clear here that Gray
wolves tend to act as buffers against recent impacts of global warming by helping
to prolong the timing for scavenger to better respond and adapt to changing
conditions. Elsewhere, however, climate change has led to increase snowfall in
wetter regions, which has affected wolf and moose population dynamics.
Wolf-Moose, Moose-Fir Dynamics
In a study undertaken in Isle Royale National Park, USA, it was clear that Gray wolves have responded to increases in
snowfall related to changes in NAO (North Atlantic Oscillation) by hunting in
larger packs. As a result of to greater killing efficiency, the number of local
moose population (Alces alces) is
three times more likely to be killed daily in comparison to years with less
snowfall when Gray wolves hunted in smaller packs. However, the impact does
not stop just quite yet… It was found that the decline in moose population led to a reduction in herbivory and browsing pressure on fir trees and saplings –
which have resulted in an observational increase in balsam fir (Abies balsamea) locally.
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| Gray Wolves hunting and chasing a Bull Moose in Isle Royale National Park |
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| Gray Wolves hunting in packs in Isle Royale National Park |
Clearly, we are
just starting to understand the interactions between top predators (in this
case Grey Wolves) and recent climate patterns across the globe. In Yellowstone
National Park, Grey Wolves tend to alleviate/buffer against the effects of
rapid climatic changes on scavengers’ food availability. In Isle Royale,
behavioral responses of Grey Wolves to changes in snow depths have led to
changes in predator-prey relationship amongst 3 trophic levels: wolves– moose- fir. Together these evidences
begin to give insight into the expected changes that may potentially occur to
boreal ecosystem due to effects of climatic changes on top predators. Obviously there will be ‘winners’ and ‘losers’ with
species increasingly trying to adapt to climate change. However, should we pay
extra attention to those that occupy a place at the top of the trophic level
and interfere with the changes in species interaction observed?
Some argue that it is
important to interfere within the changes in species interactions observed, but
clearly these responses have been generally positive. Hence in my opinion, we
should leave the local ecosystems and changes in species interaction observed alone
just yet, as I believe they will find a way back to a equilibrium/stable state
from the new condition caused from changes in species interaction, unless there
have been major changes that are damaging certain endangered species.
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| We need to survey species interaction! There are too many ways... |
Although these cases do not show
how certain keystone predators have been endangered by climate change (rather
they have responded generally positively here!), I do believe that it is vital
to invest our resources into protecting and managing species at a higher
trophic level as a focus for managing the entire community (sort of like
top-down management style). This is
because they are generally the central supporting element in local ecosystems,
and as mentioned, they cause direct/indirect cascading effects on
other trophic levels that we may or may not have observed yet. The first step in doing this I believe is to
obtain more information on keystone predators (as our overall knowledge is
generally poor). Department of Environment, Climate Change and Water NSW have
suggested that this includes obtaining more information on their
identification, how they interact with climate change and their ecology/biology
in order to develop further adaptation and management.
What are your
opinions?
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