Observed Responses: Phenological Changes?

Recent climate changes, with particular large shifts in spring temperatures around temperate regions have resulted in clear observation of phenological responses by a large range of species. Many organisms have responded by advancing the timing of their annual seasonal activities, including the timing of flowering in plants, reproduction by amphibians, the emergence of butterflies and insects, and the timing of when birds nest and migrate.

Phenological Stages of Trees

Warmer spring temperatures since 1970s have resulted in advances of tree phenology by approximately 8 days in the northern hemisphere, causing an earlier peak in the abundance of insects. Due to the earlier availability of food sources, many species of birds have advanced their breeding and egg laying date. Crick et al 1997 examined the dates of 65 bird species’ first eggs laid between 1971 to 1995 and found that there was a significant advance in the egg laying dates of 20 species by an average of 8.8 days.  For species that shifted their nesting dates earlier, they generally stand a better chance in survival as it allows them to secure their food supply earlier than competitors, but also due to the prolonged period before reaching winter season, the survival of newborns are enhanced.

Birds Breeding in the UK

Likewise, another major shift observed in recent years has been the changes in arrival time of migrant bird species to Europe and the British Isles. One particular example is the Swallow, where records suggests their arrival time advances by approximately 1.6 to 1.8 days per every 1 degrees rise in temperature. Similarly, the arrival time of Sand Martins (Riparia riparia) closely correlates with recent rise in temperatures, with a steady earlier trend in arrival observed since 1960s – as shown in the graph below. 

Graph showing mean Sand Martin (Riparia riparia) arrival time at 3 Welsh bird  observatories: Skokholm, Bardsey, Skomer.
Note: The slightly late arrival trend in the 1970s correlates with a period of cooler spring temperature recorded in the 70s

The Sand Martin!

Conversely, species that have not responded in shifting their annual cycle earlier are at a higher risk of extinction, as they become unsynchronized with the phenology of their food sources. Long distance migrant species are in particularly vulnerable in adapting to climate change in this sense.  Some species are hampered by the fact that the timing of their spring migration depends on endogenous rhythms and environmental stimuli not related to climate conditions, like day length. Similarly, sometimes temperatures in breeding and wintering regions are changing at a different pace, which can also prevent bird species from responding sufficiently.

One prime example of a bird species being adversely affected from climate change is the long distance migrant bird, the Pied Flycatcher  (Ficedula hypoleuca). Pied Flycatchers normally spend their winters in dry tropical forests in West Africa, and migrate to European temperate forests during breeding seasons. Records suggests that between 1980-2000, they have significantly advanced their mean egg-laying date by approximately 10 days, but have not made significant changes to their arrival timing on their breeding grounds during spring. 

A proper adaptation is hampered because their decision for spring migration is triggered by day length that is not related to changes in climate conditions and spring temperatures in Europe (their breeding area). Hence, by being unsynchronized and arriving at an inappropriate time to fully exploit their food supply, they will lose out as their competitors arrive at an earlier timing to optimally exploit the food source available. Thus, many have suggested that this factor, as a result of climate change, may have partly led to the decline of the Pied Flycatcher in Europe during the past few decades.

Migration route of Pied Flycatcher (Red Region: Breeding
 Areas, Green Region: Where they spend their winter)

The Pied Flycatcher!

Again, this has shown how there are both winners and losers in response to a warmer climate. So far, we have clear evidence that climate change, more specifically temperature, has a large impact on phenology of species, including their reproduction, distribution, survival and abundance. As such, with the availability of historical data, phonological events can be seen as a climate indicator and an important element in monitoring species responses to climate change at the regional, national and international scale.  Since climate change has also significantly affected rainfall distribution and pattern, in the future, one of the possibilities for further research can be to examine how rainfall might affect the phenology of biodiversity around the world.  

What are your opinions?

WAIT… What? Climate Change Sending Plants DOWNHILL not up?

Normally when you think of shifting altitudes of plants in response to climate change, you would probably expect plants to move uphill for cooler elevations in response to their physiological needs.

You’re correct to an extent. There have been many examples of shifts in tree lines and plants to higher elevations during the 20^th century. A few from the many observations include: higher altitude shifts in vegetation at the Swedish Scandes Mountains, as well as the 1-4 meters shift in elevation per decade of Alpine plants in the European Alps, and an average of 65 meters shift upwards of plants in Southern California’s Santa Rosa Mountains within 30 years……. and the list goes on!

Surprise! The Answer is........ Both!

However, here’s the plot twist: one recent study I came across suggest that in contrasts to what most people would expect … plants also move downhill in response!                                                                                           

                           
                         
  Water Availability Is Key

Portion of California used in study (~177,000 km2 )

A study in Science compared records of altitudinal distribution of 64 plant species in Northern Californian mountain ranges taken in 1930, and the same information taken in 2011. Unexpected results showed that instead of moving uphill due to rise in regional temperature, the elevation of plant species decreased by approximately 80 meters. It was suggested that the downhill movement was likely driven by species’ niche tracking of changes in regional climatic water balance – the balance between lost of water to evaporation and water gained from rainfall - instead of temperature.  This is due to the increases in precipitation and snowfall in California since 1930s that has resulted in a decreased climatic water deficit and an increase in water availability at lower elevations than ever before, resulting in the pattern of downward shifts in species that prefer

wetter, lower areas.

Plants on the Mountain Ranges of Northern California

Northern Californian Mountain Ranges
where plants are shifting downhill!

I guess this certainly reminds us that temperature is not the only factor defining species’ distribution. It clearly shows that understanding and estimating future temperature trends is not enough, we also need to pay attention to how other factors like precipitation may alter and how this, in turn, will affect regional water balance and the types and abundance of species present. Understanding how they respond is crucial, as plants play an important role for many ecological communities around the world by providing services, such as habitat and food. 

Hope you liked this short post! See you all next week! :) 

Responses from Keystone Predators - Gray Wolves

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.

Gray Wolf in Lamar Valley, Yellowstone National Park

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.

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.

Gray Wolves hunting and chasing a Bull
Moose in Isle Royale National Park

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.

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?