First things first, Merry Christmas! Hope everyone had wonderful day. The blog post today is going to be christmassy themed to hopefully keep you all in the spirit of christmas, at least till the new year when coursework deadlines will be deeming. To begin to set the mood, before you read on and discover the wonders of christmas holly (Ilex aquifolium) give the song a listen and dance around. Christmas day itself may have passed but the christmas holidays are still upon us.
Now we have you all in the mood, let me introduce today's topic 'English Holly' or sometimes known as 'Christmas Holly'. I did not realise that this seemingly harmless festive tradition is also a problematic invasive species in some areas such as in America and Pacific Northwest. Ilex aquifolium is a broad leaf evergreen shrub that can grow from 5-18 metres high. With its pretty waxy leaves and red berries, it has become, in Britain, to epitomise the essence of christmas.
Image. English Holly with its poisonous red berries on the female plant.
The holly is shade tolerant and highly competitive with other native understory plants (Boersma et al. 2006). This particular holly has escaped into forested areas where it grows in shade or sun on well drained soils. Due to the way it can grow vegetatively or by seed, it is resilient to changes in climate. It is particularly detrimental to native plants as it is a water hog, preventing sufficient water for the surrounding vegetation. With climate change, English Holly is going to be affected much like any other species on the Earth. In the IPCC 4th report, it stated that ' English Holly would see a poleward shift of the northern margin due to increasing winter temperatures' `(WWF, n/d). The same shifting is also predicted to occur with European Mistletoe (Viscum album) which is gaining altitude in response to climate change. The study reveals that the plant has climbed 656 feet in the last hundred years (National Geographic, 2010).
With the last post concentrated on the direct effects of sea ice loss in the Arctic, this post will look again at tithe phenomena of sea ice, but with a particular focus on the indirect impacts of Arctic sea ice disappearance. Below is a short video which aims to portray ice minimum volume from 1979 to 2013.
Sea ice loss may influence ecological dynamics indirectly through effects on species movements and disease transmission causing species to become more vulnerable. Arctic populations isolated when an ice free season occurs in the Arctic, the declining presence of sea ice could reduce inter-island migration. With the lengthening of the ice free season, genetic isolation among populations is encouraged (Post et al. 2013). For some species, sea ice can act as a barrier to dispersal, due to the lengthening of the sea ice free season will increase population mixing, reducing genetic differentiation. This impending loss of sea ice will increase contact among closely related series for which it currently acts as a mixing barrier. Hybridisation is likely to become increasingly common. Polar bears and grizzly bears may be the result of increasing inland presence of polar bears as a result of prolonged ice free seasons (Hoflinger, 2013). In Canada, the projected decrease in sea ice cover with Arctic warming, will increase contact between Eastern and Western Arctic species.
Image of a 'pizzly' the grizzly-polar bear hybrid.
A second indirect impact is changes that occur in animal behaviour as a result of sea ice loss. In the Canadian Arctic, later ice seasons and increased shipping traffic due to the lengthened ice free seasons could prevent migration of the Dolphin and Caribou (Poole et al. 2010). It is widely understood by ecologists that migration can decrease the likelihood of parasitism. The changes in ice formation within the Arctic could change the amount of parasite loads among the Dolphin migration herds. However, sea ice loss is not always looked on negatively, with the reduction of sea ice promotion migration hence preventing disease epidemics where the sea ice provides a corridor for pathogen transmission (Post et al. 2013).
Sea ice loss also effects terrestrial ecosystems including especially, land adjacent to the sea ice. Arctic warming, delayed freeze season and sea ice loss will promote permafrost warming increasing terrestrial primary productivity. There has been increases in the abundance and cover of shrubs occurring across the Arctic.
1) Vegetation in the Arctic is greener with a longer growing season.
2) Wildlife and large land mammal populations continued declining trends with Caribou having unusually low numbers.
3) Sea ice extent in September 2013 was the sixth lowest since observations began in 1979.
4) Northward migration into the Arctic of fish such as Atlantic Mackerel and Atlantic Cod.
This report shows that recently there has been increased concerns over this region of sea ice loss. With the academic community trying to understand how extensive the impacts of sea ice loss are. With conditions changing for many species in the Arctic, it is important to note that sea ice decline is not itself solely responsible for many individual species decline, however it plays a role with a combination of other factors. Declining sea ice is not uniform and therefore individual species responses will remain varied (Mueter and Litzow, 2007).
As we can see from the last two posts, sea ice loss can have both negative and positive effects on the ecological diversity of the Arctic. Keep your eyes peeled for the next post which will offer some insight into a completely different area of global biodiversity, one that is extremely threatened- freshwater biodiversity.
Hi all, hope everyone is having a good start to their reading week. I am currently in the process of writing my next blog post which will focus on biodiversity and urbanisation. Personally, I find this topic extremely interesting (hence why it seems to be taking so much time to collaborate my many pages of reading notes. I think I went slightly overboard on the whole reading around the topic!). Are you excited yet? Well if the thought of biodiversity makes you yawn with boredom... here is a short video to get you anticipating tomorrows big reveal.
The key questions that I aim to explore in tomorrows post are: 1) What is urbanisation? 2) Do cities have rich or poor biodiversity? 3) How is urbanisation harmful to biodiversity? 4) Is it possible for buildings to restore nature? 5) Can increased urbanisation lead to increased invasive species? 6) Are new schemes being adopted to conserve biodiversity in the age of unregulated urban sprawl? Enjoy and keep an eye out tomorrow!
The focus for today is invasive species. Before I start chattering on about zebra mussels and the red squirrel, I believe it is crucial to understand just how scientists define and quantify biodiversity. The term 'biodiversity' originates from conservation biology and was coined by Walter Rosen in 1985. A formal definition was published by the Convention of Biological Diversity (1992) which stated:
'Biodiversity is the variability among living organisms including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems'.
Biodiversity measures have, however, also taken a battering over the years. Wilson (1992) discussed the ambiguity surrounding measures of diversity and explored the possibility that biodiversity was in fact restricted by measuring species numbers alone. This has also been reiterated more recently by (McCann, 2007). Nowadays there is still uncertainty when quantifying biodiversity (scientists can never make up their minds) and therefore this will be considered in much greater detail in a few weeks.
So now back to the purpose of this post- 'INVASIVE SPECIES'. Although known worldwide as threatening and disruptive, non-native species and their impacts to biodiversity continue to be greatly debated throughout scientific literature. So why do invasive species have such a bad reputation? Invasive, known also as 'alien' and 'non- native' species can have significant effects on the existence of some species and their habitats. An example is the native red squirrel (Sciurus vulgaris) which has become threatened and outcompeted in the UK by the non-native 'grey' squirrel (Sciurus carolinensis). The first evidence of the red squirrel dates back to the end of the last ice age, 10,000 years ago.
Save our native: The Red Squirrel
However, since the grey squirrel became introduced to the UK in the 19th Century it has replaced the red squirrel throughout most of England, Wales and parts of Scotland and Ireland (Bryce, 1997). The traditional explanation for this reduction in the red squirrel, is the overwhelming competition with the grey squirrel for food resources (Kenward and Holm, 1993). This was not the only reason for their gradual decline, another proposal is the introduction of devastation parapoxvirus (a fatal strand of squirrel "pox") that was brought from North America to the UK by the grey squirrel. The disease spread into the red squirrel population hence the rate of infection was extremely high. This induced a population crash, reducing the crowding pressures on non-native grey squirrels which subsequently increased in numbers (Gurnell et al. 2004).
Squirrel distribution maps from 1945- 2010 showing the interaction between the red and grey squirrels (RSST, n/d).
From the above maps, the red squirrel population can be seen to be rapidly declining especially in Northern England and Wales, with the grey squirrel taking over the South of England and the Eastern Coast of Wales. Wales and the the midlands, surprisingly, have habitats which are occupied by both species. From the maps above it is highlighted that urgent steps are needed to address the issue of invasive species in order to save native species.
It is not just terrestrial ecosystems that can become jeopardised by non-native species, freshwater habitats are also extremely vulnerable. The ICAIS (International conference on aquatic invasive species) 2013 report stated that 'the introduction and spread of invasive species in freshwater and marine environments is a worldwide problem that is increasing in frequency'. A recent example is the invasion of the Asian Carp throughout the river systems of Illinois, USA. They were introduced, from China, into water treatment ponds to remove algae in 1970s. The carp escaped and migrated northwards through the Mississippi and Illinois rivers. Although the carp did not cause any extinctions of native species, there was a decline of certain commercial fish such as the big mouth buffalo (Ictiobus cyprinellus).
Bigmouth buffalo threatened...
Invasive species (in some cases) are considered such a colossal threat because they have the upper hand when resources become scarce. CSIRO, Australia's national science agency calls invasive species 'one of the greatest threats to biodiversity and to the ecological and economic well being of society and the planet'.
However... not every scientist shares the same assertive view on invasive species. In fact, only a week ago Professor Phil Roberts from the University of York published a paper which throws all opinions up in the air. This is why I love science, its contestable nature. Roberts (2013) discusses how the Anthropocene could raise biological diversity through the introduction of non-native species causing evolutionary hybridisation. He acknowledges that some invasive species damage ecosystems and can eradicate resident species (as I have already explored). However, his discussion remains focused on how people fail to acknowledge that invasive species can also be positive for biodiversity. On average, less than one native species dies out for each introduced species that becomes established. Roberts (2013) neglects cases of invasive species disruption and instead highlights that, despite the fact that we are losing irreplaceable populations, in some (some being the key word here) regions biodiversity is actually increasing.
I will leave you with Roberts (2013) departing words:
'we have to rethink our "irrational" dislike of invading species'.
I, on the other hand, do not believe that the negative reputation of invasive species is 'irrational', due to the destruction they can and have previously caused. However, it is vital to understand both arguments in order to judge whether there is still hope for biodiversity, in particular at a regional level, despite the doom and gloom of inevitable global species decline.
Anthropocene 0-0 Biodiversity
What do you think is in the lead? Suggestions welcome!
Despite my initial inhibitions, I have finally joined the blogging world (enter applause here). Since this is my first post, I am going to explain the focus of my blog and why I believe it warrants such discussion. As my title, 'Is the grass greener on the other side?' suggests, I will be investigating debates surrounding the Anthropocene and its effect on global biodiversity. Are we entering a 6th mass extinction or is there still hope for the species that roam our planet? Roberts (2013) discusses how the Anthropocene has brought an age of 'ecological transformations' and my blog will explore the impacts of these 'transformations' for global biodiversity. My reasoning for choosing this focus, is probably due to my slight obsession with ecology (I love plants, what can I say).
So what is the Anthropocene I hear you say? A simple definition can be found in the Oxford English Dictionary:
'relating to or denoting the current geological age, viewed as the period during which human activity has been been the dominant influence on climate and the environment'.
As is suggested, the Anthropocene is unlike any geological period before. The dangerous levels of industrialisation, land use change, ocean acidification, freshwater eutrophication, carbon dioxide and methane emissions are what distinguish this 'Age of the Humans'. Humanity has taken on the role of God and is now pushing the Earth over planetary boundaries. The exact time when the Anthropocene emerged still remains a highly contentious debate. For a VERY basic explanation of the Anthropocene and its implications, feel free to watch the following short video.
Over the course of my blog I aim to cover a wide range of topics including (but not limiting myself to) invasive species, ecosystem resilience, migration of species with climate change, ocean acidification, freshwater eutrophication and the 6th mass extinction. Rather than having a strict agenda, I want my blog to be an engagement with current literary debates and allow my opinions freedom to develop over the next 3 months.
I hope you enjoy following the battle between biodiversity and the Anthropocene. What will come out on top? Will the grass for biodiversity be greener on the other side?
