Troubling Transformation In Arctic – But Little To Do With Ice!

Some of you guys doing GEOG3057 may have received an email from Anson on an event called ‘Hot and Bothered? Species Vulnerability to Climate Change’  held by ZSL. It sounded interesting and I wanted to step away from my dissertation for a bit, so I decided to go. Though it wasn’t the main focus of the talk, what captured my attention was the brief touch (literally 2 mins max.) on ‘Arctic Greening’ by Dr. Richard Pearson from UCL. Following on Tuesday’s post on shifting vegetation and biomes, I thought it would be nice to add on to it.

Dr. Richard Pearson giving his speech on Arctic Greening (Author's Photo)

Dr. Richard Pearson showing his research on present day (2013) and projected shifts (2050s onwards) in Arctic Vegetation

‘Arctic Greening’  - Most Recent Observations

The current pattern we are increasingly observing in the Arctic is ‘greening’. This trend coincides with the increase in Arctic temperatures (hence shrubs, plants, lichens are loving it!), which have rapidly risen twice as much as the global rate. Way back during the Early Holocene, increases in temperature in the Alaskan Arctic led to one or more large-scale shrub invasions in the region suggesting that vegetation in the region are most likely able to respond to climate changes very rapidly.

If you are skeptical, here are some concrete evidence of photographs showing an increase in vegetation cover in Alaskan Arctic. The first set of photographs shows an increase in density of shrub patches and an expansion of shrubs into areas that were shrub-free in the same location at Ayiyak River between 1949 and 2000.

The Ayiyak River in 1949 and 2000
Note: Point A and B are in the same location in both photographs 

The second set of photographs below shows the arrival of spruce stands (A) and an increase density of shrubs (B).

The Kugururok River in 1950 and 2000
Note: Point A and B are in the same location in both photographs 

Future Predictions

So what does the future hold for Arctic landscapes?  Well, we will never be a 100% sure, but using statistical and ecological niche models, Dr. Richard Pearson and his fellow researchers predicts that potentially more than half (48-69%) of the vegetated regions will likely result in a change of physiognomic class, and woody plantations may increase up to 52% under climate change predictions for 2050s and restricted tree dispersal. Specifically, Alaska’s North Slope that is currently dominated by graminoids (grasses) will potentially be encroached by low-shrub and dwarfshrub tundra. There will also be a massive expansion of tree cover in regions, such as Northern Siberia.

Present observed (left) and predicted distributions of vegetation in 2050s (right) near the Arctic.  

(a. showing Siberia, b. showing Alaska, c. showing Western Canada)

What will it mean?
Continued ‘greening’ in Arctic will create/enhance positive climate feedbacks. For example, increases in woody vegetation will likely enhance evapotranspiration rates and atmospheric water vapour, which will act as a positive feedback to regional heating. An increase in darker woody plantations will reduce albedo and result in positive feedback to warming. The consequences of the shift would also create impacts beyond the Arctic, as many  species migrate seasonally from the lower latitudes in search for open space, such as ground-nesting birds.  

But wait for it… there are some positives in light of all the negatives
In the arctic region, increase shading derived from the increase in shrub canopy will reduce temperatures of soils, which may potentially slow carbon release from melting of permafrost, hence, acting as a negative feedback to global warming.

Short and brief, but hope you liked it! Have a great reading week guys! :) 

Shifts in Biomes!

Hello everyone!

I was going through some articles yesterday and I found this diagram on the right that nicely summarize some ideas I intend to focus on in my blogs. It shows a range of ‘climate’ change mechanisms that are likely driving responses from biodiversity (pink box), and potential impacts/responses from different levels of biodiversity (blue box).  The reason why I highlighted ‘climate’ because there are other factors that we must never forget, such as land use change, exploitation of resources and so on…. that are also driving recent responses observed!

Today I’ve chosen to focus on the bottom of the diagram (ironically at the very top of the biodiversity chain) – BIOMES. Unlike last week, I am going to explore at a higher level of biodiversity, and how climate change is affecting vegetation communities worldwide that can potentially be devastating enough to have an impact on biome integrity.

 Predicted aspects of Climate Change (Pink box) 

and examples of potential effects on different levels of biodiversity (Blue Box) 

What are Biomes?

For those that haven't crossed paths with this term, biomes are essentially large geographical areas with flora and fauna (plants and animals) that have common characteristics due to similar climates over a range of different continents. They are often defined by abiotic factors, such as soil types, climate patterns, relief, and vegetation. Here’s a simplified map version of major biomes on earth:

                                             Simplified version of major biomes on earth

Importance of Biomes

One of the main concerns of anthropogenic climate change has been the potential response from terrestrial biosphere. It is not surprising owing to its importance for us, such as supplying us with timber, food and other life essential… as well as for ecosystem around the world. It plays a large role in maintaining biodiversity, carbon sequestration and feedbacks in the biosphere. Changes in vegetation structure will largely influence the balance and equilibrium of the ecosystem; for example, it could influence runoff and hence the amount of seasonal streamflow; as well as habitats that will modify species interaction and trigger widespread responses from the ecosystem.   

Climate changes and its impacts on biomes

There are considerable evidence that suggest anthropogenic climate change is already driving changes in vegetation structure, distribution and productivity. The underlying effect of global warming on vegetation structure mainly resides in the biochemical and physiological influences of temperature, atmospheric CO2 concentration and water availability on terrestrial plant growth. In warmer regions, it is predicted that forest dieback may occur and terrestrial plants may face water stress due to the increases in temperature (causing faster evapotranspiration) and a potential reduction in precipitation in certain regions. Whereas, in mid-to-high latitude areas that are more chilly, predicted rise in temperatures will cause a longer growing season and an increase in vegetation productivity (NPP).  But also, other factors such as increases in wildfire and changes in climate that exceed the physiological thresholds for vegetation may alter plant mortality and recruitment in an area. The replacement of more dominant and resilient species that are able to tolerate the changing conditions can result in an entire shift in biome of an area. Therefore, as global warming continues to take place, how vegetation patterns will change is expected to vary considerably amongst different regions.

Current Shifts

It is clear that climate change is shifting vegetation both latitudinally and elevationally worldwide. Researchers at University of California, Berkeley estimated that between 1901-2002, mean temperatures increased significantly on 76% of land worldwide, especially in subarctic, temperate and boreal ecosystems. Biome shifts that have been noticeable include dieback of trees and retracting of woodlands to grasslands in the Sahel, reducing ecosystem services it brings to many people (forest wood for cooking / supply of water) in that region. Nevertheless, the noticeable process of shrublands encroaching onto Arctic tundra is also a huge problem for many endangered species.

Picture showing a mixture of grassland
 and woodland - shifts observed in Sahel

Map showing the Sahel region

However, one of the main concerns that ecologist and scientists have raised are ‘tipping points’, where exceeding ecosystem thresholds may potentially cause irreversible shifts and changes in major biomes. A study showed that tropical biomes, such as rainforest, desert and savanna in Africa and South America are tied to certain climate tipping points, where when climate thresholds exceed they don't gradually shift through intermediate states, but rather ‘tip over’ where they suddenly switch to other ecosystems.

Future predictions

In terms of future predictions, Alo and Wang (2008) simulated 8 different GCMs climate projections with a global vegetation model to estimate changes in vegetation near 2100. They found a consistent pattern of poleward expansion and treeline shift of boreal and temperate forests towards higher latitudes at the expense of tundra and alpine ecosystems across all the GCM scenarios. They also suggest that a widespread vegetation degradation in the tropics will occur, especially in South Africa and South America due to an increase in drought deciduous trees at the expense of evergreen trees due to changing moisture conditions.

Similarly, Lapola and his colleagues’ analysis on potential future distribution of biomes in tropical South America suggests that increases in carbon dioxide concentration and/or drier season persists longer than four months, then Amazonian rainforest could likely be replaced by drier biomes, such as shrublands, tropical savannahs and even semi-deserts.

Picture showing Amazonian Rainforest.... that in the future could potentially look different from a shift to drier biomes

… To avoid this we need to manage!

To avoid this, adequate adaptation measures must be put in place according to vulnerability by ecologist. But also a significant reduction in greenhouse gas emission must be made to avoid the potential devastating consequences to global vegetation – which also will have potential impacts on wildlife, species interaction, biosphere feedbacks and last but not least...our (human) well-being! 

Personally I think that instead of focusing on individual species (not saying that they aren't important), but maybe we should focus more on researching/mitigating/managing biomes and ecosystems. If we can't secure ecosystems and habitats that are deemed as essentials for species, then many species without adequate adaptability mechanism will lose out giving that some ecosystems are tied to certain 'tipping points'. What do you think? 

Anyways! Have a great week and see you all in a few days :)  

Shifting Latitudes - North Sea Fishes

Globally, spatial distributions of fish stock are increasingly shifting in latitude as well as depth. Although arguably intensive fishing pressures plays a role, however, patterns observed recently are most likely attributed to recent climate change and increases in seawater temperature. It is widely known that changes in sea temperatures may influence fishes through their growth, reproduction and their food web from changes at other trophic levels. Species having limited dispersal capability of responding to the changes or have troubles finding a suitable habitat may potentially face widespread extinction. Research has shown species that recently responded to the changing conditions tend to have faster life cycles and smaller body size than non-shifting species – meaning that some species are currently losing or might lose out in the future!

                                                               Shoal of Fish Migrating!

Allison Perry and her colleagues noted that temperatures of the North Sea water have increased by an average of 0.6 degrees between 1962-2001. Their research showed that Atlantic cod (Gadus morhua), scaldfish (Arnoglossus laterna), snakeblenny (Lumpenus lampretaeformis) and common sole (Solea solea) have all shifted northwards with a distance ranging from 48 – 403 kilometers (WOW!). 403 kilometers seems as though a huge but unsurprising number, as the rates of migration are likely much higher than other wildlife (such as butterflies) since they are less likely to face barriers and constraints during the process.

   Snakeblenny 

Similarly, Engelhard and his team examined historical and contemporary fisheries data and revealed that current distribution of North Sea cod – located mainly in northeastern parts of the North Sea is entirely opposite to the distribution in 20^th century, where they were mainly found in the west, just off the coast of England and Scotland. They suggested that the northward shift is likely due to warming, however, intensive fishing pressures have likely caused the eastward shift shown.  

     North Sea Cod

Future estimation by UK Climate Impacts Programme suggested that North Sea water temperatures are predicted to increase by 1 to 2.5 degrees by 2050. And it has been suggested that blue whiting, redfishes and many more species may completely retract from the North Sea by 2050!  Sad :/