Phenology

The Phenology Network is a charity organisation that has been recording the first sightings/buddings/flowerings of different species since the 18th century.  It was founded by Robert Marsham in 1736 and was carried on by his family until 1958.  Marsham recorded 27 different events for over 20 different species, i.e. the first snowdrop flowering, the first migratory birds arriving and the first croak of the frog [1].

Since then, hundreds of other people have recorded similar events over the last two centuries either as a hobby or as a volunteer of the Woodland Trust and/or Royal Meteorology Society.  These events have been recorded all over the UK and can be used to identify changes in flowering and migration dates of many different species as an indicator of climate change.  Scientists have used this data to build up a record of these events over the last 250 years.  Amano et al published a paper on changes in flowering dates in the past 250 years and how climate has affected these [2].  It was calculated that each 1 degree increase in temperature meant plants flowered 5 days earlier on average.  

The first flowering of plants and budding of trees can greatly affect whole ecosystems.  Some migratory birds rely on climate to time their migration periods, however most species of birds time their migration with day length.  As day length doesn’t change with temperature rise, most migratory birds are still migrating on the same day they always have and therefore are at risk of prey having already been eaten due to the earlier migration of other birds.  This can indirectly cause shifts in distribution of species as they become more dominant in areas where prey is available at a later date.

References:

[1] http://www.naturescalendar.org.uk/

[2] Amano, T, R. Smithers, T. Sparks and W. Sutherland (2011), 'A 250-year index of first flowering dates and its response to temperature changes', Proceedings of the Royal Society, 277, 2451-2457.

Invasive Species and Disease

Perhaps one of the most important and deadly consequences of climate change is the effects warming will have on invasive species and the spread of disease.
Invasive species are species which are introduced to an area (e.g. by humans or climate change), are able to survive and breed there and consequently create competition with native species often out competing them.  Invasive species can also been seen as pests, such as certain species of insects, which then eat/damage crops and harm wildlife.  Invasive species can spread disease easily from one area to another - for example mosquitoes and ticks.

Climate change is warming the planet.  Areas that were previously too cold for ticks and mosquitoes to survive in are now warm enough for them to invade.  This will increase in the years to come as temperatures increase globally.  Virus carrying insects are becoming more and more prevalent in areas previously inhabitable [1].  These diseases are likely to affect not only animals but humans as well.  The likelihood of animals viruses being contracted in humans will also increase as the number of different viruses as well as the spread of each increases [2].
Areas as far as the Arctic are set to be affected by the spread of disease.  As Arctic marine temperatures increase, the number of fish pathogens has also increased.  Fish under stress due to warming conditions are more susceptible to these pathogens.  As sea ice reduces, summers become longer and milder.  These new conditions allow increased growth of larvae and parasitic larvae.  Bacteria caused disease, free living viruses and disease brought in by migratory birds are also all set to increase. [3].
The biggest cause of increased disease is change in species range - mostly those of virus carrying insects, ticks and mosquitoes.  There are many factors that counteract the increase in disease carrying insects, however, humans should prepare for more numerous and frequent disease outbreaks in the upcoming future.

References:
[1] http://www.sciencedaily.com/releases/2011/06/110629102150.htm
[2] http://news.bbc.co.uk/1/hi/sci/tech/7657415.stm
[3] Bradley et al (2005), 'The potential impact of climate change on infection diseases of Arctic fauna', International Journal of Circumpolar Health, 64, 468-477.

Killer whales and Gentoo penguins

Last night was the last episode of Frozen Planet! It has been an AMAZING series and now I've decided I'm definitely going Polar travelling after Uni!

Last night's episode was called 'On Thin Ice' and investigated the impact of climate change on the poles and how this has effected the wildlife living there.  A lot of the wildlife in the poles is at risk due to climate change as their way of life on the sea ice has to change.  The 30% reduction in sea ice that has been seen since satellite records began in the 1970s has a large impact on polar wildlife.  For example, polar bears need sea ice to hunt on - with this massive reduction it means they have to return to land and their summers without food are longer and longer.
However, it is not all negative for polar wildlife - some species are now able to occupy new areas that they couldn't previously.  Killer whales (Orcinus orca) have thinner blubber and larger dorsal fins than other polar whales.  These features prevent them from moving too poleward as the presence of sea ice is too much of a challenge to swim under with their large fins.  However, since the reduction in sea ice, a significant change has been seen in the sightings of Killer whales.  The increased number of sightings further inland than before suggest that larger populations of Killer whales are now able to live and hunt in these areas previously covered in ice. [1],[2].
Another example of species thriving in these new conditions include the Gentoo Penguins (Pygoscelis papua) which were previously known to inhabit warmer islands north of Antarctica.  In the last few decades, the number of these penguins seen around the Antarctic Peninsular has increased significantly.  This is due to the warming of the seas around the peninsular and the reduction in sea ice. [1]

If you haven't been watching frozen planet...go to BBC Iplayer NOW while the whole series is still online!

References:
[1] BBC Frozen Planet (http://www.bbc.co.uk/iplayer/episode/b00zj39j/Frozen_Planet_On_Thin_Ice/)
[2] Higdon, W & S. H. Ferguson (2009), 'Loss of Arctic sea ice causing punctuated change in sightings of killer whales (Orcinus orca) over the past century', Ecological Applications, 19, 1365-1375.

Habitat Fragmentation

Habitat fragmentation is when a natural habitat is disrupted or divided, leaving an area of that habitat that is hard/impossible for certain species to cross.  Examples of these include rivers, roads, deforested areas, damns, crop fields etc.  Humans are constantly changing the natural environment by adding these features which then have a negative effect on species in the habitat.  Habitat fragmentation is especially important with migrating species (i.e. birds) and those species that have started to shift polewards due to climate change.  Shifting northwards is not always possible for species as they depend on food sources and certain habitat conditions, however those species that are able to adapt to other conditions are being prevented from moving north due to habitat fragmentation.

For example, the Bog turtle (America's smallest turtle) may be prone to extinction in the near future as it has very specific habitat requirements (bogs and wetlands) which are not only scarce but are often sandwiched in between main roads and areas of housing [1].  These act as barriers for the slow ground moving turtle, making it very hard to migrate to any other areas.

Another example is bird populations.  A study by Melles et al analysed the range expansion of bird species in the last 20 years.  It was found that fragmentation (such as deforestation and treeless areas) caused expansion rates to be slower than in areas without fragmentation.  The main reason for this lag in expansion is due to low breeding success and smaller populations (of species and their prey) existing in fragmented areas [2].

HOWEVER scientists have recognised this problem and there is a lot of research and conservation work being done on habitat fragmentation and assisted migration of species.  In California, mountain lions are being tagged in order to observe and understand their movements around fragmented areas (i.e. areas with roads, housing, water and concrete) [3].  A study like this can aid scientists with the knowledge on how to build wildlife corridors, allowing migration and range expansion of species in the light of climate change.  Currently there are lots of conservationists working on the idea of assisted migration as a means to save endangered species globally.

References:


[1] http://news.nationalgeographic.com/news/091211-ten-threatened-species-animals-global-warming-pictures/#/bog-turtle_10582_600x450.jpg
[2] Melles, S.J., M.J. Fortin, K. Lindsay and D. Badzinski (2011), 'Expanding northward: influence of climate change, forest connectivity, and population processes on a threatened species' range shift', Global change biology, 17, 17 - 31.
[3] http://www.newscientist.com/article/mg21028094.000-on-mountain-lion-patrol-in-the-california-wilds.html

Interglacial refugia?!

A couple of blogs ago I was talking about glacial refugia and how, during glacial periods, expanding ice cover forced species to migrate southwards in order to reach warmer climates. This is a natural phenomena and species have always adapted to climate change in the past. However, is there such thing as 'interglacial refugia'?! Do species in the sub-polar regions have to move closer to the poles during interglacial warm periods?!

The answer is - YES.

In the past, during glacial periods, cold adapted species such as the arctic fox had much larger populations than present. This was because as the climate became colder and ice cover increased, these species had larger areas to live and breed in and so their populations increased (expansion without rear contraction). Then, as ice started to melt and the earth shifted into an interglacial, these species could no longer survive in these warming areas and were pushed back towards the poles. The interglacial we are currently experiencing has reduced populations and contracted ranges of polar species.

Noone is quite sure when the current interglacial is going to end, some scientists say it should have already ended while others say it has around another 10,000 years to go. However, the number of species currently moving north due to climate change has no reflection on interglacial refugia. Present rates of northward movement are much higher than any known rates of expansion/contraction in the past.

References:

[1] Stewart et al (2011) 'Refugia revisited: individualistic responses of species in space and time', Proceedings of the Royal Society, 277, 661 - 671.

Tree line expansion?

A bit of late night journal reading led me to an article about tree line expansion due to climate change. The idea that areas currently covered in ice could become suitable environments for new trees and shrubs to grow in the near future is a positive impact of climate change! New trees = increased uptake of CO2!

The study was taken in Sweden near the tree line which marks the boundaries of the Arctic. The image on the left shows the shrub colonisation of the area in 1977 (top) compared with 2009 (bottom). As temperatures have increased here, we can see that increased amount of vegetation can grow here. Research has found that although models predict this expansion could happen along the entire Arctic boundary, some areas are showing no new vegetation despite ideal conditions...

However, surely this northward expansion of vegetation is only a good thing?! Except of course the decreased albedo due to ice melt...which I personally think can be solved by everyone painting their roofs white?!

References:

Rundqvist et al (2011), 'Tree and shrub expansion over the past 34 years at the tree-line near Abisko, Sweden', Journal of the human environment, 40, 683 - 692.

Bridging the Gap: The Holocene

The Holocene is an interesting time period to investigate as it is more like our present climate than during the Pleistocene where mass extinctions and migrations occurred between glacials and interglacials. During the Holocene, we experienced periods of cooling (little ice age) and periods of warming (medieval warming period). The warming periods can be useful in understanding as they are the closest to the climate change we are currently experiencing. Bruyn et al wrote a paper this year called ‘Faunal histories from Holocene ancient DNA’ which looks at the changes in species, distribution and migration during the Holocene. DNA can be used to calculate the genetic diversity of a species at any given time. A large diversity of a particular species suggests a larger population, perhaps allowed by migration and expansion without rear contraction. An example of this is the Elephant seal which colonised new southern areas during the Holocene and increased its population and genetic diversity.

However, the Holocene also gave rise to many species extinctions due to its variability in climate. During the late Holocene period this was most apparent as habitats were degraded due to climate variability, including the southern elephant seals’ newly found habitats. (Talking of elephant seals, did anyone see that graphic fight between them on Frozen Planet last week?!)

Although climate triggered migrations were apparent during the Holocene and Late Glacial Maximum, these migrations were often on a smaller and/or slower scale than any migratory movements seen within the last century due to climate change.

References:

1. Bruyn et al 2011, ‘Faunal histories from Holocene ancient DNA’, Trends in ecology and evolution, 26, 8, 405 – 413.

Glacial Refugia

Recent climate change may be causing species to migrate northwards but this is not the first time in the long history of our earth that changes in the climate have caused mass migrations. It seems that species have been able to adapt to climate variations in the past in the exact same way as now – by migrating to areas of the earth that are more suitable in terms of temperature and habitat. The most well-known example of this is Glacial Refugia. During the Last Glacial Maximum (LGM), many species in the Northern Hemisphere had to migrate southwards in order to escape the cold temperatures and increasing ice cover that was occurring in the higher latitudes [1]. Evidence for this migration can be found by investigating the biodiversity and genetic variation of species in refugia sites. Refugia sites were found in Europe and Asia, where temperatures were warmer, and the effects of glaciation were less apparent. These sites are sometimes referred to as ‘hybrid zones’ as migration of different species (previously in allopatry) allowed interbreeding and introduced hybrid species [1].

I’ve just finished reading an article on the glacial refugia of marine fish by Kettle et al. In the paper they have looked at migration during the LGM and at various other points throughout the Holocene in order to understand and predict future migration due to climate change. Identified fish remains, leftover from human consumption, is the main proxy used in this study in order to determine the past ranges of different species. Studies like this have great importance for the future of the fishing industry, however, like the science of climate change they are still very vague and migration is difficult to predict. Patterns from the past show possible migration to areas of low oxygen concentration and high sea ice despite these conditions being seen as too severe for certain population (i.e. Salmon and cod) to inhabit [2].

Investigations of past species migration are important to gain an understanding of climate induced movement – however, as with all studies that are based on proxies and occurred thousands of years ago, there is a large grey area of uncertainty which reflects the future of our planet through climate change. On top of this, migration during the LGM may have been easier as there were less areas of habitat fragmentation preventing movement.

References:

1. Feliner 2011, 'Southern European glacial refugia: A tale of tales', Taxon, 60, 365 - 372.
2. Kettle et al 2011, 'Refugia of marine fish in the northeast Atlantic during the last
glacial maximum: concordant assessment from archaeozoology and palaeotemperature reconstructions', Climate of the past, 7, 181 - 201.

Beetles, butterflies and how pole-ward migration works

The movement of species towards the poles is not as simple as individual organisms migrating further north. The actual phenomenon involves a decrease in population in the southern ends of a distribution of species (extinction due to warmer temperatures) and an increase in colonisation rates of the same species in the northern end of a distribution (including new areas which are now warm enough to host these species) [1]. This shows a gradual shift in the population of a species which correlates which global temperature rise. This pole-ward migration is likely to affect all types of species, however, airborne species are far more likely to be able to shift northward than slower land moving species due to habitat fragmentation. For example, animals such as birds are likely to be able to cross boundaries such as barren land (increasing with climate change!) and urban areas to habitats more suitable to live in. Slow moving creatures such as snails, for example, may find moving their distribution northwards a much more difficult task.

Butterflies are a good example as many species have already shown a great northward movement – however, other species may find it more difficult to move north due to how delicate and sensitive they are to habitat fragmentation (and not being able to fly long distances). In a study of 35 UK butterflies, 63% were found to have moved north significantly in the last century (35 – 240km) [1]. However, some scientists have been looking at ‘assisted colonisation’ of certain butterfly species. This term means that humans can help to relocate declining butterfly species into new habitats which are suitable for colonisation but they may not naturally be able to reach [2]. This is one way we may be able to reduce the loss of biodiversity from the impact of climate change over the next few decades.

Lastly, it is not such a bleak future for our bio diverse world. There are some species which will expand their range northward without contracting their southern range – increasing their distribution into new areas without their loss in others. An example of this is a species of ground beetle called Agonum viridicupreum which has been found to have expanded its range northward by about 100km in the last century without any loss of population in the southern range [3].

References:
[1] Parmesan et al 1999, 'Poleward shifts in geographical ranges of butterfly species associated with regional warming', Nature, 399, 579 – 583.
[2] http://planetearth.nerc.ac.uk
[3] Drees et al 2011, ‘Poleward range expansion without a southern contraction in the ground beetle Agonum viridicupreum (Coleoptera, Carabidae)’, ZooKeys, 100, 333-352.

Grizzly-Polar Bear Hybrid!

An interesting impact of northward migration! Polar bears and grizzly bears are a close enough match of DNA to mate but under normal circumstances they would never interact in the wild. However, the first hybrid has been found in the wild - and the most likely cause of this is climate driven as grizzly bears move northwards!

References:

http://news.nationalgeographic.com/news/2006/05/polar-bears_2.html

The Real Story

Species all over the world are moving northwards and upwards in order to reach colder climates to live in. To put it simply, climate change is real and happening - whether caused by humans or natural processes, it has warmed the planet by approximately 0.8C in the last century (NASA - [1]). Within this time period, over 2,000 species have moved significantly northward or upward (i.e. tree ranges have shifted up mountains) in order to reach their optimum conditions to live [2]. As their original habitats become warmer, species can no longer survive due to increased temperatures or in some cases lack of food as their sources of prey have moved north. In either case, the ultimate consequence is to move northward to colder conditions and prey sources. However, for many species this is difficult as they could be slow ground movers as opposed to species such as birds and butterflies. I will cover the obstacles many species have to overcome in order to migrate north in another blog.

References:

[1] http://www.nasa.gov/vision/earth/environment/2005_warmest.html

[2] Parmesan et al 1999, 'Poleward shifts in geographical ranges of butterfly species associated with regional warming', Nature, 399, 579 - 583

Guillemots facing extinction?

To begin my blog I want to start off with something simple - a short video from the National Geographic. It shows the impact global warming has had on the polar regions, witnessed by a man who goes there every year to count the population of guillemots. The three main points the video makes are:

1. Reduction in pack ice has decreased the number of Arctic cod which the guillemots feed on.

2. A general increase in the area has led to an increase in other birds which increases the competition for the small number of Arctic cod left.

3. Polar bears are left stranded in this area due to pack ice reduction and so have begun to eat a large number of guillemots.

These are just a few impacts of global climate change. The fact is, in the last decade more than 2000 species are thought to be moving north at a rate of 15 feet per day to escape the increase in temperatures due to global warming [1]. In this blog I will be looking at different species that have successfully migrated north, and those that are at risk of extinction due to habitat fragmentation and physical boundaries such as oceans that prevent this movement. I will look at past examples of species migration and how we can learn from these to predict the bleak future of our bio-diverse planet.



References:

[1] http://news.discovery.com/animals/animals-migrating-north-global-warming-110818.html