Online Climate Change Connection 3.1: Climate Change and the Development of Novel Biomes

Biomes contain a collection of plants, animals, and microorganisms that have similar climate tolerances and therefore overlapping geographic ranges associated with specific temperature and precipitation conditions (see Figure 3.4 in the textbook). A major emphasis of Unit 1 is the importance of physiological tolerance of the physical environment as the ultimate determinant of where a species can exist. In addition, species’ geographic distributions are subject to biological interactions such as competition and predation, as well as dispersal ability, which will be considered in Units 2, 3, and 4.

Although discussion of climate change usually focuses on temperature, patterns of precipitation have changed as well. Simultaneous changes in temperature and precipitation of differing magnitudes may result in the occurrence of climate combinations that are not currently found on Earth. These “novel” or “non-analog” climates could cause a reshuffling of organisms due to their climate tolerances, resulting in the appearance of biomes that do not occur today. For example, two species occurring under current climate conditions may have different ranges of precipitation where they can occur, despite similar temperature tolerances. Under a warmer, drier climate, one species may drop out of the biome, one may remain, and a new species may occur due to its ability to tolerate the drier conditions (Figure 1).

A graph plots temperature versus precipitation for three species, A, B, and C, by current and future climate. The species are represented as ovals on the graph. C lies on the left of the graph, only slightly intersecting A on the right. B intersects both C and A. Current climate is an oval between B and A. Future climate is an oval between C and B.
Figure 1  Potential Influence of Climate Change on Three Co-occurring Species  Over time, the current climate in a region may become hotter and drier, extending beyond the range of temperature and precipitation in the current climate (as indicated by the solid ellipses). Species A, which has a range of tolerance indicated by the dotted ellipsis surrounding it, will not be able to occur in the new climate. However, Species B will able to remain. Species C, which is not able to occur in the current climate, will be able to exist in the new climate. As a result, a new collection of species may occur, with different dominant species or growth forms, creating a novel biome. (After S. T. Jackson and J. T. Overpeck. 2000. Paleobiology 26S: 194–220.)

Such change in climate conditions and associated novel biomes are known to have occurred in the past (Overpeck et al. 1992; Jackson and Williams 2004). During the period of deglaciation following the last ice age, climates with greater seasonal temperature changes than those of today occurred. Several novel biome types occurred in association with these climates (Figure 2; see also Figure 25.16), including an association of spruce and ash trees not found in any biomes today (Williams et al. 2001).

A map of North America shows novel assemblages in the country by years before present. The data from the graph are as follows.
- 21,000 years before present: small patches in the north-eastern parts of the United States.
- 16,000 years before present: large patches in the north-eastern parts of the United States and small patches in the north-western parts of Canada.
- 14,000 years before present: larger patches in the north-eastern parts of the United States and large patches in the north-western parts of Canada.
- 12,000 years before present: smaller patches in the north-eastern parts of the United States and larger patches in he north-western parts of Canada.
- 6,000 years before present: no clear patches in North America.
Figure 2  The Occurrence of Novel Plant Assemblages Following the Last Glaciation Novel assemblages are indicated by the red colors; the darker the red, the greater the difference from any assemblages found today. The past vegetation was reconstructed using preserved pollen found in bogs and lakes. (After J. W. Williams and S. T. Jackson. 2007. Front Ecol Environ 5: 475–482.)

What can we expect in the future as climate continues to change? Will novel combinations of climate variables occur? John Williams and colleagues (Williams et al. 2007; Williams and Jackson 2007) examined the potential for the appearance of novel climates using models of future climate change from the report of the Intergovernmental Panel on Climate Change (IPCC 2007). They evaluated the uniqueness of predicted future climates relative to today’s climates using mean summer and winter temperatures and mean summer and winter precipitation, as these variables are particularly important to plant survival and establishment. Novel climates were determined by whether the climate differed from existing climates in a 500 km (300 mile) radius around a target region. Their analysis indicated that large areas of Earth would experience novel climates by the end of the twenty-first century (Figure 3). The appearance of these novel climates was particularly pronounced in the tropical and temperate zones. In addition, the predicted trajectory of greenhouse gas emissions influenced the occurrence of novel climates, with greater emissions resulting in more area experiencing a novel climate.

Four flat world maps show projected occurrences of novel climates across the world by the end of the twenty-first century. The legend shows the following color codes: dark blue, between 0 and 0.25; light blue, between 0.25 and 0.5; yellow, between 0.5 and 0.75; and red, between 0.75 and 1.
The first graph shows a global scenario A 2. Most countries are dark blue. There are small patches of yellow and red in northern South America, north-western Africa, the Middle East, some countries in South-East Asia, and parts of northern Australia.
The second graph shows global scenario B 1. Most countries are dark blue. There are small patches of light blue in northern South America, north-western Africa, the Middle East, some countries in South-East Asia, and parts of northern Australia.
The third graph shows a 500 kilometer limit for scenario A 2. North America and Europe are mostly light blue with some patches of dark blue in Europe. All other countries are mostly red with some patches of yellow.
The fourth graph shows a 500 kilometer limit for scenario B 1. North America, southern South America, Europe, and Asia are mostly dark blue. Northern South America, Africa, and some South East Asian countries are yellow with some patches of red.
Figure 3 The Projected Occurrence of Novel Climates by the End of the Twenty-First Century The color scale indicates the probability that a future climate will not have a modern analog, with 0 being the lowest and 1 being the highest, under two scenarios: Scenario A2, in which emissions of greenhouse gases continue to increase at their current rate and reach 850 ppm by 2100, and Scenario B1, in which the rate of greenhouse gas emissions decreases and stabilizes at 550 ppm by 2100. The projection also differs depending on whether the future no-analog climates are determined by comparisons with the current global scale (top two panels) or relative to existing climates found within a 500 km radius around a given location (bottom two panels). (After J. W. Williams and S. T. Jackson. 2007. Front Ecol Environ 5: 475–482.)

We can get a sense of the potential for the emergence of novel biomes by examining the initial stages of vegetation responses to climate change. In particular, multiple reports of vegetation change in the Arctic indicate that parts of the tundra are shifting toward a shrub-dominated biome (Sturm et al. 2001; Epstein et al. 2008; Elmendorf et al. 2012). Birch and willow shrubs are increasing in abundance throughout the lower-latitude portions of the Arctic. The increase in shrub cover corresponds with the substantial warming that has been recorded over the past two decades (Macias-Fauria et al. 2012) and is also consistent with warming experiments carried out in Alaskan Arctic tundra (Chapin et al. 1995). It is also reflective of vegetation patterns that occurred during warming in the early Holocene, about 10,000 years ago (Anderson and Brubaker 1993).

Literature Cited

Anderson, P. M. and L. B. Brubaker. 1993. Holocene vegetation and climate histories of Alaska. In Global Climates since the Glacial Maximum, H. E. Wright, J. E. Kutzbach, T. Webb III, W. F. Ruddiman, F. A. Street-Perrott and R. J. Bartlein (eds.), 386–400. University of Minnesota Press, Minneapolis.

Chapin, F. S., G. R. Shaver, A. E. Giblin, K. J. Nadelhoffer and J. A. Laundre. 1995. Responses of arctic tundra to experimental and observed changes in climate. Ecology 76: 694–711.

Elmendorf, S. C. and 47 others. 2012. Plot-scale evidence of tundra vegetation change and links to recent summer warming. Nature Climate Change 2: 453–457.

Epstein, H. E., D. A. Walker, M. K. Raynolds, G. J. Jia and A. M. Kelley. 2008. Phytomass patterns across a temperature gradient of the North American Arctic tundra. Journal of Geophysical Research 113, G03S02, doi:10.1029/2007JG000555.

IPCC. 2007. Climate Change 2007The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge.

Jackson, S. T. and J. T. Overpeck. 2000. Responses of plant populations and communities to environmental changes of the late Quaternary. Paleobiology 26S: 194–220.

Jackson, S. T. and J. W. Williams. 2004. Modern analogs in Quaternary paleoecology: Here today, gone yesterday, gone tomorrow? Annual Review of Earth and Planetary Sciences 32: 495–537.

Macias-Fauria, M., B. C. Forbes, P. Zetterberg and T. Kumpula. 2012. Eurasian Arctic greening reveals teleconnections and the potential for structurally novel ecosystems. Nature Climate Change 2: 613–618.

Overpeck, J. T., R. S. Webb, and T. Webb III. 1992. Mapping eastern North American vegetation change of the past 18 ka: No-analogs and the future. Geology 20: 1071–1074.

Sturm, M., C. Racine and K. Tape. 2001. Climate change: Increasing shrub abundance in the Arctic. Nature 411: 546–547.

Williams, J. W. and S. T. Jackson. 2007. Novel climates, no-analog communities, and ecological surprises. Frontiers in Ecology and the Environment 5: 475–482.

Williams, J. W., B. N. Shuman and T. Webb III. 2001. Dissimilarity analyses of late-Quaternary vegetation and climate in eastern North America. Ecology 82: 3346–3362.

Williams, J. W., S. T. Jackson and J. E. Kutzbach. 2007. Projected distributions of novel and disappearing climates by 2100 AD. Proceedings of the National Academy of Sciences USA 104: 5738–5742.