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.
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:
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?
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 :)
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