Earth Gauge » Plants and Animals

Climate Fact: Japan Bloom Dates

administrator — Wed, 08 Oct 2008 21:44:16 +0000

Since 1953, the dates when Japan’s plants bloom in the spring have been arriving progressively earlier in the calendar year, and the dates when the trees change color and lose their leaves in the fall have been arriving progressively later. The average date when the country’s famous Cherry trees bloom is now arriving an average of 4.2 days earlier in the year, while Apricot trees are blooming an average of 5.4 days earlier, Camellias an average of 9.4 days earlier, and Dandelions an average of six days earlier. These trends correspond to increases in average spring temperatures. Additionally, the trends are most pronounced for plants growing in Japan’s big cities, which highlights how the Urban Heat Island Effect, or the tendency for cities to be warmer than surrounding rural areas, affects plant life. During the fall, the trends are essentially the opposite. Compared to the 1950’s, the leaves on Ginkgo and Japanese Maple trees are changing color an average of 10.7 and 15.4 days later in the year, respectively.

Season: Spring

Source: Japan Meteorological Agency (2007). “Long-term trends of phonological events in Japan: Summary of ‘Report on Climate Change 2005.’” Accessed Online 18 April 2008 ds.data.jma.go.jp/tcc/tcc/news/PhenologicalEventsJapan.pdf

Climate Fact: Tanganyika Troubles

administrator — Wed, 08 Oct 2008 21:03:22 +0000

One of the most important sources of animal protein in East Africa is being threatened by rising temperatures. Over the past few decades, the average air temperature in the region around Africa’s Lake Tanganyika (which sits on the borders of Congo, Zambia, Tanzania and Burundi) has warmed by about one degree Fahrenheit. This has corresponded to an increase in the lake’s surface temperature and a decrease in the average regional wind velocity. These trends have made the water in the lake more stable. This means that there is less mixing, which moves nutrients around in the water and prevents them from settling on the lake bottom, where they are inaccessible to most life. The recent slow-down in water movement has resulted in a decrease in available nutrients and 20 percent decline in the total mass of phytoplankton, tiny organisms that use the sun’s energy to build bodies out of these nutrients and ultimately feed all other life in the lake. This decline in phytoplankton mass has translated into a 30 percent decline in the fish yields that come out of the lake. Until recently, Lake Tanganyika supplied 25 to 40 percent of the animal protein consumed by the populations in the four countries it borders.

Seasons: Winter, Spring, Summer, Fall

Source: O’Reilly, CM et al. “Climate change decreases aquatic ecosystem productivity of Lake Tanganyika, Africa.” Nature 424 (2003): 766-768.

Climate Fact: Lake Baikal Trends

administrator — Wed, 08 Oct 2008 20:58:27 +0000

The Earth’s largest and oldest lake, Russia’s Lake Baikal, provides habitat for over 2,500 species, most of which are found nowhere else on Earth. Baikal has changed rapidly over the last 60 years. These changes include a two degree Fahrenheit rise in the temperature of the water, a corresponding 300 percent increase in chlorophyll concentration in the Lake, and a 335 percent increase in the zooplankton populations that feed on chlorophyll-producing algae. Additionally, the average number of days per year when ice covers Baikal has fallen by 18 days over the past 100 years. This ice provides habitat for species of diatom, which sink to the Lake bottom as the ice retreats, where their bodies provide critical nutrients for species living in the depths. Few places on Earth have experienced such changes in species composition and seasonal timing at the rate that Lake Baikal has.

Seasons: Winter, Spring, Summer, Fall

Sources: Hampton, SE et al. “Sixty years of environmental change in the world’s largest freshwater lake- lake Baikal, Siberia.” Global Change Biology: Accepted May 2008 and Gardner, Timothy. “Lake warming faster than air.” – news.com.au 1 May 2008. Accessed Online 2 May 2008 http://www.news.com.au/story/0,23599,23628417-2,00.html

Climate Fact: Rodent Reorganization

administrator — Wed, 08 Oct 2008 20:55:25 +0000

In Southeast Arizona, there has been a marked increase in wintertime rainfall since 1977, which has resulted in a three-fold increase in shrub cover. Prior to this period, grasses had dominated the region’s vegetation system. As the shrubs have moved in, so have species of small pocket-mice, which are replacing large kangaroo rats. One species of kangaroo rat went locally extinct in 1994, and its disappearance was immediately followed by a colonization of pocket mice. Populations of these pocket mice have been growing exponentially since. An extreme rainfall event in 1999 caused flooding and helped to promote this general trend, as kangaroo rats are poor swimmers and more than 90 percent of their population in the area drowned during the flood.

Season: Wintertime

Source: Thibault, KM and Brown, JH. “Impact of an extreme climatic event on community assembly.” Proceedings of the National Academy of Sciences 105 (2008): 3410-3415.

Climate Fact: Diatoms and Dinoflagellates

administrator — Wed, 08 Oct 2008 20:44:46 +0000

During the warm seasons (spring through fall), the water in the Baltic Sea is stable and stratified. This means that the warmest and least dense water is on the surface, and as you dive deeper and deeper, layers of progressively colder, saltier, and denser water are encountered. During the decades of the 1970’s and 1980’s, the North Atlantic Oscillation (NAO) was in a negative phase, and winters in the Baltic Sea were generally cold and dry. As a result, during the winter, the water on the surface would cool to the point where it was colder than the water below it, and mixing between the layers would occur until a new stable state (one where the cold water is on the surface) was reached. This annual mixing was important for the survival of the sea’s diatoms, which depended on the mixing that would take place during the spring as the sea reverted from the winter to summer water column formation. Diatoms are photosynthetic, single-celled organisms, which form a large part of the marine food pyramid’s base. A positive state of the NAO since the late 1980’s has corresponded to milder winters, and the deep mixing that would occur as the seasons changed no longer occurs. As a result, the diatoms that depend on the mixing have been largely replaced by another type of single-celled organism known as dinoflagellates, which may be best known for their whip-like tails that propel them through the water. This change has also corresponded to other changes in the sea’s species’ composition.

Seasons: Winter, Spring, Summer, Fall

Sources: Alheit, J. et al. “Synchronous ecological regime shifts in the central Baltic and the North Sea in the late 1980’s.” ICES Journal of Marine Science 62 (2005): 1205-1215 and Hinrichsen, HH et al. “Correlation analyses of Baltic Sea winter water mass formation and its impact on secondary and tertiary production.” Oceanologia 49 (2007): 381-395.

Climate Fact: Ice Break-Up Dates and Bears

administrator — Wed, 08 Oct 2008 20:36:11 +0000

Polar bears, Earth’s largest land predator, are most common on annual sea ice that sits over shallow seas. This ice provides the bears with a platform from which they can hunt for food. In Canada’s Western Hudson Bay region, which is at the southernmost extent of the polar bear’s range, winter and spring are the best times to hunt, as that is when there is the most ice cover and spring is when the most seals are available. By the time late spring and summer arrive, the Hudson Bay is ice-free, and the bears are essentially stranded from their prey until the ice freezes-up again. The bears must live on their fat reserves during this period, which generally lasts about four months. The earlier the ice breaks up in the spring, the less time the bears have to build fat reserves to survive the hungry periods. Warmer temperatures in the region mean that the ice is now breaking up an average of three weeks earlier than it did 30 years ago, and a correlation exists between the date of the break-up and starvation induced mortality in young and older bears. Overall, the region’s Polar Bear population declined from 1194 in 1987 to 935 in 2004. While healthy adult bears can usually survive the extra stress of earlier ice break-up, years when ice breaks-up especially early generally correspond to more human-bear encounters, as the bears stray from their usual territories to find food.

Seasons: Spring, Summer

Source: Regehr, EV et al. “Effects of Earlier Sea Ice Breakup on Survival and Population Size of Polar Bears in Western Hudson Bay.” The Journal of Wildlife Management 71 (2007): 2673-2683.

Climate Fact: Spruce Beetle Surge

administrator — Wed, 08 Oct 2008 20:20:57 +0000

While forests fires may be the most visible and dramatic events that reshape North America’s forests, outbreaks of insect “pests” actually affect an area 45 times larger than that affected by fire. Generally, insects attack trees weakened by things like drought, wind storms, and fire, as healthy trees are usually able to fend-off attacks from pests. If the pests attack the tree in large enough numbers, however, the tree’s natural defenses can become overwhelmed. Spruce beetle populations become “outbreaks” when there is a large enough population of already weakened host trees (more than two clumps of five trees in a five acre area) and the right climatic conditions. In America’s Intermountain region, the right climate conditions for an outbreak include winter temperatures that do not drop below negative 29 degrees Fahrenheit (the temperature at which beetle larvae freeze to death), warmer fall temperatures (which allow the beetles to have more life cycles in a shorter period of time), and several years of drought (which weaken trees). Since 1976, there has been a 5.4 degree Fahrenheit increase in average wintertime temperatures and a 3.4 degree Fahrenheit increase in average autumn temperatures in the Intermountain Region. Also, the percentage of the western United States that is in drought condition has doubled over the past century.

Seasons: Winter, Spring, Summer, Fall

Sources: Logan, JA et al. “Assessing the impacts of global warming on forest pest dynamics.” Frontiers in Ecology and the Environment 1 (2003) 130-137 and Hebertson, EG and Jenkins, MJ. “Climate Factors Associated with Historic Spruce Beetle (Coleoptera: Curculionidae) Outbreaks in Utah and Colorado.” Environmental Entomology 37 (2008) 281-292 and “U.S. Temperature and Precipitation Trends.” U.S. National Oceanic and Atmospheric Administration (NOAA): Climate Prediction Center. 5 January 2005. 26 June 2008 < http://www.cpc.ncep.noaa.gov/charts.shtml> and United States. Climate Change Science Program. Weather and Climate Extremes in a Changing Climate. Synthesis Assessment Product 3.3: GPO. 2008.

Climate Fact: Forest-Tundra Dynamics

administrator — Wed, 08 Oct 2008 20:14:10 +0000

In northern Québec, patches of Black Spruce forests exist alongside the arctic shrub tundra, forming an ecological zone known as forest-tundra. Heavy winter snows, short frost-free growing seasons, and high winds limit the possible area in which Black Spruce trees can grow. These harsh conditions also limit how tall these trees can grow, and in the zones where climate conditions are just tolerable enough for the trees to survive, the spruces will grow in bushes as opposed to upright trees in order to limit their exposure to the elements. Since the 1980’s, when a twenty year regional cooling trend ended, spruce shrubs that had previously been limited by high wind and low temperatures have grown taller throughout the forest-tundra zone.

Seasons: Winter, Spring, Summer, Fall

Source: Gamache, Isabelle and Payette, Sergei. “Height growth response of tree line black spruce to recent climate warming across the forest-tundra of eastern Canada.” Journal of Ecology 92 (2004): 835-845.

Climate Fact: Mid-latitude Moths and Mating

administrator — Wed, 08 Oct 2008 20:05:10 +0000

In the mid-latitude climates, insect species have a dormant period during the cold winter months, meaning that there is a limited period of time throughout the year when they can reproduce. In regions where there is little seasonal difference in rainfall and temperature, such as in the equatorial rainforests, insects do not have a dormant period and most species produce multiple generations each year. For many (but not all) mid-latitude insect species, the number of generations a species will have each year is dependent upon the temperature, especially in the spring. The earlier in the year the temperature stops dropping below freezing (the beginning of the frost-free period or growing season), the earlier in the year insects can lay eggs that are likely to survive until they hatch, and the more generations they can have. The grape berry moth, a native of eastern North America, is one species that makes use of warm springs to have more generations of offspring. In years when the cumulative average temperature is below 61 degrees Fahrenheit, most individual grape berry moths will have two generations. In years when the temperature exceeds 61 degrees, however, many individuals within the species will have three generations.

Seasons: Spring, Summer

Source: Tobin, PC et al. “Historical and projected interactions between climate change and insect voltinism in a multivoltine species.” Global Change Biology 14 (2008): 951-957.

Climate Fact: Seabird Shift

administrator — Wed, 08 Oct 2008 20:00:36 +0000

Climate variability in the mid- to high-latitudes of the Northern Hemisphere, or the area from about 35 degrees North to the poles, is largely controlled by two naturally occurring climate oscillations, the Pacific Decadal Oscillation (PDO) and the North Atlantic Oscillation (NAO). In 1977, both oscillations shifted from negative to positive phases, which resulted in a warming of the ocean waters in the northeastern Pacific around Alaska, and a cooling of the waters in the northeastern Atlantic around Scandinavia. This shift in sea surface temperatures (SSTs) was one of the largest ever recorded. In 1989, the opposite trend happened. The magnitude of this shift, however, was much less pronounced. The population trends of two species of seabird, the Common Murre and the Thick-billed Murre, were studied in relation to these shifts. These species thrive under essentially the opposite environmental conditions. The large magnitude shift in 1977 caused populations of both species to decline throughout the entire hemisphere, while both populations grew after the smaller shift in 1989. Because these shifts produced opposite trends in local environmental conditions, it might be expected that one species would thrive and one species would decline in number during each of the regime shifts. Since this was not the case, this phenomenon illustrates how it can be difficult for top predatory species to adapt to any rapid climatic fluctuation.

Seasons: Spring, Summer, Fall

Source: Irons, D.B. et al. “Fluctuations in circumpolar seabird populations linked to climate oscillations.” Global Change Biology 14 (2008): 1455-1463.

Climate Fact: Chinook Survival

administrator — Wed, 08 Oct 2008 19:34:02 +0000

Did you know that 75 percent of the water resources in the West originate from snowmelt? Mountain snowpack accumulates over the winter and as it melts during the spring, summer, and fall, it feeds the region’s rivers and streams. Over the last half of the 20th Century, November to March temperatures in the Pacific Northwest rose by about 4.5 degrees Fahrenheit. This trend has corresponded to less snowpack, an earlier melting of snowpack, and more late winter and early spring precipitation falling as rain instead of snow. Between 1950 and 1998, the average date when there ceased to be snow on the ground advanced 16 days earlier in the year, and the point in the year when river levels peak is now arriving an average of nine days earlier than it did in the 1950’s. This trend in earlier peak flow also means that average autumn stream levels are lower than they were 50 years ago, and that the water in these streams is warmer. Salmon are cold water species, and cannot tolerate significant rises in temperature. Low stream levels impede their ability to navigate the waters, and also generally mean poor water quality. The high-elevation streams in Idaho’s Salmon River watershed host populations of juvenile Chinook salmon, which remain in these streams for a year before venturing into larger water bodies. Fall stream flow is the most important climatic factor for estimating juvenile survival rates, which largely control Pacific Chinook salmon populations.

Seasons: Summer, Fall

Sources: “HydroFacts.” Southwest Journal of Hydrology 6 (2007): 13 and Mote, P.W., A.F. Hamlet, M.P. Clark, and D.P. Lettenmaier. 2005. Declining mountain snowpack in western North America. Bull. Amer. Met. Soc. 86:39–49 and Groisman, P.Y., P.W. Knight, and T.R. Karl. 2001. Heavy precipitation and high streamflow in the United States: Trends in the 20th Century. Bulletin of the American Meteorological Society 82:219-246 and Crozier, L. and Zabel, R.W. “Climate impacts at multiple scales: evidence for differential population responses in juvenile Chinook salmon.” Journal of Animal Ecology 75 (2006): 1100-1109.

Climate Fact: Carbon Catch in the Amazon

administrator — Wed, 08 Oct 2008 19:26:48 +0000

Since at least the late 1970’s, trees in the Amazon have been growing faster despite the fact that climbing vines (lianas), which grow on trees as parasites and sap their energy, have also increased in number and spatial extent. This growth means that the rate at which each hectare (2.47 acres) in the Amazon takes carbon dioxide (CO2) out of the atmosphere has been increasing by about one metric ton (2200 pounds) per year since 1975, a trend can be largely explained by an increase in available atmospheric CO2, of which concentrations have grown from 280 parts per million in pre-industrial times to around 386 parts per million today. Another factor that helps to explain this faster growth is an increase in sunlight over the region during the last 30 years. More sunlight means more available energy for photosynthesis, the process through which plants use energy from the sun to convert atmospheric carbon into chemical energy and living matter. Increases in nitrogen and phosphorous (two key plant nutrients) deposition on the area, as a result of more burning and more dust blowing over the Atlantic from the Sahara, may also be contributing to the increased plant growth.

Seasons: Winter, Spring, Summer, Fall

Sources: Baker, TR et al. “Increasing biomass in Amazonian forest plots.” Philosophical Transactions of the Royal Society of London B 359 (2004): 353-365 and Phillips, OL et al. “Changes in the Carbon Balance of Tropical Forests: Evidence from Long-Term Plots.” Science 282 (1998): 439-442 and Phillips, OL et al. “Pattern and process in Amazon tree turnover, 1976-2001.” Philosophical Transactions of the Royal Society of London B 359 (2004): 381-407.

Climate Fact: Pinatubo and Photosynthesis

administrator — Wed, 08 Oct 2008 19:15:15 +0000

The June 15, 1991 eruption of Mt. Pinatubo, which sits on the island of Luzon in the Philippines, injected between 31 and 44 billion pounds of sulfur dioxide (SO2) into Earth’s stratosphere (the second layer of the Earth’s atmosphere). This layer of SO2 circled the globe in about three weeks, and by the end of 1991 had made its way to the Polar Regions. The layer formed an “aerosol envelope,” which absorbed incoming solar radiation, making the stratosphere warmer than average (by about seven degrees Fahrenheit in the tropical stratosphere), and the surface cooler than average (by about one degree Fahrenheit). Another effect of this eruption was a reduction in the rate of atmospheric carbon dioxide (CO2) increase. This effect has been attributed to a general planetary increase in the rate of photosynthesis, or an increase in the rate at which plants use energy from the sun to convert atmospheric CO2 into chemical energy and plant matter. While more sunlight is generally conducive to plant growth, plants use “diffuse” radiation more effectively than they do direct radiation. The sulfur dioxide in the stratosphere helped to make the sunlight that reached the plants at Earth’s surface ideal for plant growth. At one forest site, total photosynthesis in 1992 (the year when sulfur concentrations in the stratosphere were at their peak) was 21 percent higher than it was under average conditions. As the stratosphere began to clear, the rate of photosynthesis, and thus plants’ uptake of carbon dioxide, began to decline. In 1993, the photosynthetic rate was six percent above average, and in 1994 it was three percent above average.

Seasons: Winter, Spring, Summer, Fall

Sources: Gu, Lianhong et al. “Response of a Deciduous Forest to the Mount Pinatubo Eruption: Enhanced Photosynthesis.” Science 299 (2003): 2035-2038 and Wolfe, Jason. “Volcanoes and Climate Change.” NASA Earth Observatory 5 September 2000. 16 July 2008 <http://earthobservatory.nasa.gov/Study/Volcano/>

Cliamte Fact: Seagrass and SSTs

administrator — Wed, 08 Oct 2008 18:43:28 +0000

The summer of 2003 was one of Europe’s warmest on record and maximum sea surface temperatures (SSTs) in the Mediterranean were well above average (by about 2.5 degrees Fahrenheit). These temperatures were the highest recorded between 1972 and 2004. Also during this period, years when the maximum water temperature was above average were years when there were above average numbers of seagrass plants flowering (these plants generally produce flowers only once every five years). In 2003, the Sea’s dominate seagrass species (Posidonia oceanica) flowered at record levels. While this phenomenon may suggest that warmer SST’s are good for seagrass, the overall warming trend in the Mediterranean of 1.7 degrees Fahrenheit since the early 1980’s has corresponded to an increase in seagrass mortality, a decline in the species’ areal extent, and a decline in rhizome growth (stalk-like plant structures that grow horizontally, usually underground) . Indeed, years of extensive flowering are often followed immediately by years of extensive mortality.

Season: Summer

Source: Diaz-Almela, E et al. “Consequences of Mediterranean warming events in seagrass (Posidonia oceanica) flowering records.” Global Change Biology 13 (2007): 224-235.

Climate Fact: White Spruces Withering

administrator — Wed, 08 Oct 2008 17:51:47 +0000

While cold temperatures limit growth for many plant species inhabiting the boreal forest and tundra regions of the northern hemisphere (from about 50 to 80 degrees North), increases in temperature can cause more evaporation from the soil and lead to drought stress. This appears to be the case with White Spruce forests in Alaska. A longer growing (or frost free) season and an increase in average May through August temperatures of six degrees Fahrenheit over the last 100 years have corresponded to decreases in annual growth rates. Large annual tree rings grew during the cool and wet period of 1915 to 1965. Since then, however, there has been a 40 to 50 percent decline in average annual tree ring width. During the cool and wet 1930’s, it was not unusual for the White Spruce trees to grow two millimeter-wide tree rings (a little more than one 16th of an inch). Today, one millimeter rings are more common. Warmer temperatures appear to be causing the soil to dry earlier in the summer, and when this happens the trees stop growing and start preparing for winter.

Seasons: Spring, Summer

Source: Barber, V et al. “Reduced growth of Alaskan white spruce in the twentieth century from temperature-induced drought stress.” Nature 405 (2000): 668-673.

Climate Fact: Copepod Range Change

administrator — Wed, 08 Oct 2008 17:28:24 +0000

The Labrador Sea Water (LWS) is a stream of cold, fresh, and oxygen rich water that travels down the western Atlantic coast from the Labrador Sea, which is located between Greenland and Newfoundland, towards the Equator. This stream forms in the late fall/early winter after the seasonal accumulation of glacial melt water, which is less dense than salt water, has pooled on the surface. As the strong northwesterly winter winds start to blow across the Labrador Sea, the fresh water pool cools, sinks to a depth of about 5,000 feet, and travels down the East Coast of Canada. The North Atlantic Oscillation (NAO), or the cyclical change in the pressure difference between the Azores High and Icelandic Low, controls the strength of these winds. During positive NAO phases (when the Azores High is particularly high and the Icelandic Low is particularly low), the winds are stronger, which leads to more cooling on the surface and a stronger flow of the Labrador Sea Water. The stronger the flow of this water, the cooler the waters along America’s east coast are. Over the last 30 years, the NAO was strongly and predominately positive, and copepod species (small crustaceans that collectively constitute the biggest source of protein in the oceans) that were previously found only in the waters off Canada, began showing up as far south as New Jersey, and increased in abundance all along the New England coast.

Seasons: Fall, Winter

Source: Johns, DG. “Arctic boreal plankton species in the Northwest Atlantic.” Canadian Journal of Fisheries and Aquatic Sciences 58 (2001): 2121-2124.

Climate Fact: Moving on Up

administrator — Wed, 08 Oct 2008 17:17:17 +0000

Southern California’s Santa Rosa Mountains, located about two hours southeast of Los Angeles, stand out as forest islands amongst the lowland desert to the east, and the chaparral scrubland to the west. Plants not capable of tolerating the hot and dry conditions of the lowlands find refuge at the cooler and wetter high elevations. Over the last 30 years, however, a two degree Fahrenheit rise in temperature, coupled with an increase in the length of dry spells (despite an overall increase in precipitation), has made it more difficult for tree species such as white fir, Jeffrey pines, and golden cup oaks to live in the lowlands. As a result, these species, as well as several other shrub and wildflower species that prefer similar temperature and moisture regimes, have been forced to move uphill. The ranges of these species’ are now an average of 213 feet higher in elevation than they were in the late 1970’s.

Seasons: Winter, Spring, Summer, Fall

Source: University of California, Irvine. “Climate change caused widespread tree death in California mountain range, study confirms.” Today@UCI 11 August 2008. 20 August 2008 http://www.today.uci.edu/news/release_detail.asp?key=1793

Climate Fact: North Sea Species Richness

administrator — Wed, 08 Oct 2008 17:06:46 +0000

While land and sea surface temperature trends are the most common measures of climate change, changes in bottom temperatures, especially in shallow seas, can have major implications for marine species. Ocean species can generally adjust their ranges more easily than land species, as there are fewer geographic barriers in the ocean and many fish species use the free energy ocean currents provide to disperse their larvae. In the North Sea, which sits between Great Britain and Scandinavia, the average wintertime bottom temperature has increased by almost four degrees Fahrenheit since the early 1970’s, a rate that is more than ten times faster than the global average. As this has happened, species that formerly could only survive in the warmer waters to the south moved into the North Sea, and species that are accustomed to the cooler temperature regimes now seen in more northerly waters shifted their ranges north. Overall, during the last 30 years, more species moved into the North Sea than moved out, and the number of fish species living in the North Sea is now 50 percent higher than it was in the early 1970’s.

Seasons: Winter, Spring, Summer, Fall

Source: Hiddink, JG and Hofstede R Ter. “Climate induced increases in species richness of marine fishes.” Global Change Biology 14 (2008): 453-460.

Climate Fact: Expanding Larch Forests

administrator — Tue, 07 Oct 2008 20:19:57 +0000

Over the 20th century in the polar region of Russia’s Ural Mountains, there was a 1.6 degree Fahrenheit rise in average summertime temperature. Cold temperatures are usually the limiting factor for tree growth at the poles and high elevations. Warming tends to allow trees to grow at higher elevations than they previously could, and also allow trees that could only survive growing close to the ground like bushes to grow upright. As the Urals have warmed, Larch forests (Larches are deciduous conifers) have moved uphill by between 65 and 200 feet, with 87 percent of the trees growing in the recently colonized areas emerging after 1970, when most of the warming trend has taken place. Also in these forests, 36 percent of the trees over 100 years in age grow like bushes, while 90 percent of the trees that have emerged since 1950 grow upright.

Seasons: Spring, Summer, Fall

Source: Devi, Nadezhda et al. “Expanding forests and changing growth forms of Siberian larch at the Polar Urals treeline during the 20th century.” Global Change Biology 14 (2008): 1581-1591.

Climate Fact: Cotton Yields and Climate

administrator — Tue, 07 Oct 2008 20:09:02 +0000

A common cotton disease in the southeast, hardlock, is caused by fungus and affected by temperature and humidity. The disease does better during years when humidity and rainfall levels are above average, especially during the months of July to September, when cotton plant flowers and bolls (pods containing 32 seeds from which the cotton fibers grow) mature. During the wet and humid year of 2002 in Florida, hardlock caused crop yields to decrease from 650 pounds per acre to 400, or 20 million dollars in lost yield. Drier and less humid years, on the other hand, discourage fungal growth and favor high yields. Over 50 percent of the variability in yields in the southeastern U.S. can be explained by climate. Years with the highest cotton yields correspond to years with lower than normal sea surface temperatures (SSTs) in the Gulf of Mexico and Atlantic Ocean, where the winds that blow into the southeast during the summer originate. These lower SSTs mean less humidity, and cause relatively dense air to become concentrated in upper air masses, which discourages convective cloud formation and rainfall.

Seasons: Summer, Fall

Sources: Baigorria, GA et al. “Assessing Predictability of Cotton Yields in the Southeastern United States Based on Regional Atmospheric Circulation and Surface Temperatures.” Journal of Applied Meteorology and Climatology 47 (2008): 76-90 and The University of Florida Education and Research Center. “Cotton/Hardlock.” Accessed Online 1 October 2008 <http://nfrec.ifas.ufl.edu/cottonhardlock.htm> and Cotton’s Journey. “The Story of Cotton.” Accessed Online 1 October 2008 <http://www.cottonsjourney.com/storyofcotton/page3.asp>