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==Further reading==
==Further reading==
*{{cite book |author=Thomas Lovejoy; Lee Hannah |title=Climate Change and Biodiversity|publisher=[[The Energy and Resources Institute|TERI]] Press |year=2006 |pages= |isbn=817993084X |ISBN-status=May be invalid - please double check}}
*{{cite book |author=[[Thomas Lovejoy]]; Lee Hannah |title=Climate Change and Biodiversity|publisher=[[The Energy and Resources Institute|TERI]] Press |year=2006 |pages= |isbn=817993084X |ISBN-status=May be invalid - please double check}}
*{{cite book |author=[[Tim Flannery]] |title=The Weather Makers: How Man Is Changing the Climate and What It Means for Life on Earth |publisher=[[Grove/Atlantic, Inc.|Grove/Atlantic]] Press |year=2006 |pages= |isbn=0802142923}}
*{{cite book |author=[[Tim Flannery]] |title=The Weather Makers: How Man Is Changing the Climate and What It Means for Life on Earth |publisher=[[Grove/Atlantic, Inc.|Grove/Atlantic]] Press |year=2006 |pages= |isbn=0802142923}}


Revision as of 06:03, 23 April 2012

Alpine Flora at Logan Pass, Glacier National Park, in Montana, USA: Alpine plants are one group expected to be highly susceptible to the impacts of climate change

Environmental conditions play a key role in defining the function and distribution of plants, in combination with other factors. Changes in long term environmental conditions that can be collectively coined climate change are known to have had enormous impacts on plant diversity patterns in the past and are seen as having significant current impacts.[1] It is predicted that climate change will remain one of the major drivers of biodiversity patterns in the future.[2][3][4]

Palaeo context

Australian Rainforest: An ecosystem known to have significantly contracted in area over recent geological time as a result of climatic changes.
Map of global vegetation distributions during the last glacial maximum

The Earth has experienced a constantly changing climate in the time since plants first evolved. In comparison to the present day, this history has seen Earth as cooler, warmer, drier and wetter, and CO2 (carbon dioxide) concentrations have been both higher and lower.[5] These changes have been reflected by constantly shifting vegetation, for example forest communities dominating most areas in interglacial periods, and herbaceous communities dominating during glacial periods.[6] It is has been shown that past climatic change has been a major driver of the processes of speciation and extinction.[1] The best known example of this is the Carboniferous Rainforest Collapse which occurred 350 million years ago. This event decimated amphibian populations and spurred on the evolution of reptiles. [1]

Modern Context

There is significant current interest and research focus on the phenomenon of recent anthropogenic climate changes, or global warming. Focus is on identifying the current impacts of climate change on biodiversity, and predicting these effects into the future.

Changing climatic variables relevant to the function and distribution of plants include increasing CO2 concentrations, increasing global temperatures, altered precipitation patterns, and changes in the pattern of ‘extreme’ weather events such as cyclones, fires or storms.

Because individual plants and therefore species can only function physiologically, and successfully complete their life cycles under specific environmental conditions (ideally within a subset of these), changes to climate are likely to have significant impacts on plants from the level of the individual right through to the level of the ecosystem or biome].

Effects of CO2

Recent increases in atmospheric CO2.

Increases in atmospheric CO2 concentration for affect how plants photosynthesise, resulting in increases in plant water use efficiency, enhanced photosynthetic capacity and increased growth.[7] Increased CO2 has been implicated in ‘vegetation thickening’ which affects plant community structure and function.[8] Depending on environment, there are differential responses to elevated atmospheric CO2 between major ‘functional types’ of plant, such as C3 and C4 plants, or more or less woody species; which has the potential among other things to alter competition between these groups.[9] Increased CO2 can also lead to increased Carbon : Nitrogen ratios in the leaves of plants or in other aspects of leaf chemistry, possibly changing herbivore nutrition.[10]

Effects of temperature

Global annual surface temperature anomaly in 2005, relative to 1951-1980 mean

Increases in temperature raise the rate of many physiological processes such as photosynthesis in plants, to an upper limit. Extreme temperatures can be harmful when beyond the physiological limits of a plant.

Effects of water

Precipitation trends in the United States, from the period 1901-2005. In some areas rainfall has increased in the last century, while some areas have dried.

As water supply is critical for plant growth, it plays a key role in determining the distribution of plants. Changes in precipitation are predicted to be less consistent than for temperature and more variable between regions, with predictions for some areas to become much wetter, and some much drier.

General effects

Environmental variables will not act in isolation, but also in combination with one other, and with other pressures such as habitat degradation and loss or the introduction of exotic species. It is suggested that that these other drivers of biodiversity change will act in synergy with climate change to increase the pressure on species to survive.[11]

Direct impacts of climate change

Changes in distributions

Pine tree representing an elevational tree-limit rise of 105 m over the period 1915–1974. Nipfjället, Sweden

If climatic factors such as temperature and precipitation change in a region beyond the tolerance of a species phenotypic plasticity, then distribution changes of the species may be inevitable.[12] There is already strong evidence that plant species are shifting their ranges in altitude and latitude as a response to changing regional climates.[13][14]

When compared to the reported past migration rates of plant species, the rapid pace of current change has the potential to not only alter species distributions, but also render many species as unable to follow the climate to which they are adapted.[15] The environmental conditions required by some species, such as those in alpine regions may disappear altogether. The result of these changes is likely to be a rapid increase in extinction risk.[16] Adaptation to new conditions may also be of great importance in the response of plants.[17]

Predicting the extinction risk of plant species is not easy however. Estimations from particular periods of rapid climatic change in the past have shown relatively little species extinction in some regions, for example.[18] Knowledge of how species may adapt or persist in the face of rapid change is still relatively limited.

Changes in the suitability of a habitat for a species drive distributional changes by not only changing the area that a species can physiologically tolerate, but how effectively it can compete with other plants within this area. Changes in community composition are therefore also an expected product of climate change.

Changes in life-cycles (phenology)

The timing of phenological events such as flowering are often related to environmental variables such as temperature. Changing environments are therefore expected to lead to changes in life cycle events, and these have been recorded for many species of plants.[13] These changes have the potential to lead to the asynchrony between species, or to change competition between plants. Flowering times in British plants for example have changed, leading to annual plants flowering earlier than perennials, and insect pollinated plants flowering earlier than wind pollinated plants; with potential ecological consequences.[19] A recently published study has used data recorded by the writer and naturalist Henry David Thoreau to confirm effects of climate change on the phenology of some species in the area of Concord, Massachusetts.[20]

Indirect impacts of climate change

All species are likely to be not only directly impacted by the changes in environmental conditions discussed above, but also indirectly through their interactions with other species. While direct impacts may be easier to predict and conceptualise, it is likely that indirect impacts are be equally important in determining the response of plants to climate change.

A species whose distribution changes as a direct result of climate change may ‘invade’ the range of another species for example, introducing a new competitive relationship.

The range of a symbiotic fungi associated with plant roots may directly change as a result of altered climate, resulting in a change in the plants distribution.

A new grass may spread into a region, altering the fire regime and greatly changing the species composition.

A pathogen or parasite may change its interactions with a plant, such as a pathogenic fungus becoming more common in an area where rainfall increases.

Increased temperatures may allow herbivores to expand further into alpine regions, significant impacting the composition of alpine herbfields.

There are innumerable examples of how climate change could indirectly affect plant species, most of which will be extremely difficult to predict.

Higher level changes

Species respond in very different ways to climate change. Variation in the distribution, phenology and abundance of species will lead to inevitable changes in the relative abundance of species and their interactions. These changes will flow on to affect the structure and function of ecosystems.[14]

Challenges of modelling future impacts

Accurate predictions of the future impacts of climate change on plant diversity are critical to the development of conservation strategies. These predictions have come largely from bioinformatic strategies, involving modelling individual species, groups of species such as ‘functional types’, communities, ecosystems or biomes. They can also involve modelling species observed environmental niches, or observed physiological processes.

Although useful, modelling has many limitations. Firstly, there is uncertainty about the future levels of greenhouse gas emissions driving climate change [21] and considerable uncertainty in modelling how this will affect other aspects of climate such as local rainfall or temperatures. For most species the importance of specific climatic variables in defining distribution (e.g. minimum rainfall or maximum temperature) is unknown. It is also difficult to know which aspects of a particular climatic variable are most biologically relevant, such as average vs. maximum or minimum temperatures. Ecological processes such as interactions between species and dispersal rates and distances are also inherently complex, further complicating predictions.

Improvement of models is an active area of research, with new models attempting to take factors such as life-history traits of species or processes such as migration into account when predicting distribution changes; though possible trade-offs between regional accuracy and generality are recognised.[22]

Climate change is also predicted to interact with other drivers of biodiversity change such as habitat destruction and fragmentation, or the introduction of foreign species. These threats may possibly act in synergy to increase extinction risk from that seen in periods of rapid climate change in the past.[11]

See also

References

  1. ^ a b c Sahney, S., Benton, M.J. & Falcon-Lang, H.J. (2010). "Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica" (PDF). Geology. 38 (12): 1079–1082. doi:10.1130/G31182.1.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  2. ^ Sala OE, Chapin FS, Armesto JJ; et al. (2000). "Global biodiversity scenarios for the year 2100". Science. 287 (5459): 1770–4. doi:10.1126/science.287.5459.1770. PMID 10710299. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  3. ^ Duraiappah, Anantha K.; World Resources Institute (2006). Millennium Ecosystem Assessment: Ecosystems And Human-well Being—biodiversity Synthesis. Washington, D.C: World Resources Institute. ISBN 1-56973-588-3.{{cite book}}: CS1 maint: multiple names: authors list (link)
  4. ^ Pressey RL, Cabeza M, Watts ME, Cowling RM, Wilson KA (2007). "Conservation planning in a changing world". Trends Ecol. Evol. (Amst.). 22 (11): 583–92. doi:10.1016/j.tree.2007.10.001. PMID 17981360. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  5. ^ Dunlop, M., & Brown, P.R. (2008) Implications of climate change for Australia’s National Reserve System: A preliminary assessment. Report to the Department of Climate Change, February 2008. Department of Climate Change, Canberra, Australia
  6. ^ Huntley, B. (2005). "North temperate responses". In Hannah, Lee Jay; Lovejoy, Thomas E. (ed.). Climate Change and Biodiversity. New Haven, Conn: Yale University Press. pp. 109–24. ISBN 0-300-11980-1.{{cite book}}: CS1 maint: multiple names: editors list (link)
  7. ^ Steffen, W. & Canadell, P. (2005). ‘Carbon Dioxide Fertilisation and Climate Change Policy.’ 33 pp. Australian Greenhouse Office, Department of Environment and Heritage: Canberra
  8. ^ Gifford RM, Howden M (2001). "Vegetation thickening in an ecological perspective: significance to national greenhouse gas inventories". Environmental Science & Policy. 4: 59–72. doi:10.1016/S1462-9011(00)00109-X.
  9. ^ Dukes JS, Mooney HA (1999). "Does global change increase the success of biological invaders?". Trends Ecol. Evol. (Amst.). 14 (4): 135–9. doi:10.1016/S0169-5347(98)01554-7. PMID 10322518. {{cite journal}}: Unknown parameter |month= ignored (help)
  10. ^ Gleadow RM; et al. (1998). "Enhanced CO2 alters the relationship between photosynthesis and defence in cyanogenic Eucalyptus cladocalyx F. Muell.". Plant Cell Environ. 21: 12–22. doi:10.1046/j.1365-3040.1998.00258.x. {{cite journal}}: Explicit use of et al. in: |author= (help)
  11. ^ a b Mackey, B. (2007). "Climate change, connectivity and biodiversity conservation". In Taylor M., Figgis P. (ed.). Protected Areas: buffering nature against climate change. Proceedings of a WWF and IUCN World Commission on Protected Areas symposium, Canberra, 18–19 June 2007. Sydney: WWF-Australia. pp. 90–6. {{cite conference}}: Unknown parameter |booktitle= ignored (|book-title= suggested) (help)
  12. ^ Lynch M., Lande R. (1993). "Evolution and extinction in response to environmental change". In Huey, Raymond B.; Kareiva, Peter M.; Kingsolver, Joel G. (ed.). Biotic Interactions and Global Change. Sunderland, Mass: Sinauer Associates. pp. 234–50. ISBN 0-87893-430-8.{{cite book}}: CS1 maint: multiple names: editors list (link)
  13. ^ a b Parmesan C, Yohe G (2003). "A globally coherent fingerprint of climate change impacts across natural systems". Nature. 421 (6918): 37–42. doi:10.1038/nature01286. PMID 12511946. {{cite journal}}: Unknown parameter |month= ignored (help)
  14. ^ a b Walther GR, Post E, Convey P; et al. (2002). "Ecological responses to recent climate change". Nature. 416 (6879): 389–95. doi:10.1038/416389a. PMID 11919621. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  15. ^ Davis MB, Shaw RG (2001). "Range shifts and adaptive responses to Quaternary climate change". Science. 292 (5517): 673–9. doi:10.1126/science.292.5517.673. PMID 11326089. {{cite journal}}: Unknown parameter |month= ignored (help)
  16. ^ Thomas CD, Cameron A, Green RE; et al. (2004). "Extinction risk from climate change". Nature. 427 (6970): 145–8. doi:10.1038/nature02121. PMID 14712274. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  17. ^ Jump A, Penuelas J (2005). "Running to stand still: adaptation and the response of plants to rapid climate change". Ecol. Lett. 8: 1010–20. doi:10.1111/j.1461-0248.2005.00796.x.
  18. ^ Botkin DB; et al. (2007). "Forecasting the effects of global warming on biodiversity". BioScience. 57 (3): 227–36. doi:10.1641/B570306. {{cite journal}}: Explicit use of et al. in: |author= (help)
  19. ^ Fitter AH, Fitter RS (2002). "Rapid changes in flowering time in British plants". Science. 296 (5573): 1689–91. doi:10.1126/science.1071617. PMID 12040195. {{cite journal}}: Unknown parameter |month= ignored (help)
  20. ^ Willis CG, Ruhfel B, Primack RB, Miller-Rushing AJ, Davis CC (2008). "Phylogenetic patterns of species loss in Thoreau's woods are driven by climate change". Proc. Natl. Acad. Sci. U.S.A. 105 (44): 17029–33. doi:10.1073/pnas.0806446105. PMC 2573948. PMID 18955707. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  21. ^ Solomon, S., et al. (2007). Technical Summary. In ‘Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change’. (Eds. S. Solomon, et al.) pp. 19-91, Cambridge University Press: Cambridge, United Kingdom and New York, NY, USA.
  22. ^ Thuiller W; et al. (2008). "Predicting global change impacts on plant species' distributions: Future challenges". Perspectives in Plant Ecology, Evolution and Systematics. 9: 137–52. doi:10.1016/j.ppees.2007.09.004. {{cite journal}}: Explicit use of et al. in: |author= (help)

Further reading

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