Assessment of Climate Change and Freshwater Ecosystems of the Rocky Mountains, Usa and Canada

Abstract

The Rocky Mountains in the USA and Canada encompass the interior cordillera of western North America, from the southern Yukon to northern New Mexico. Annual weather patterns are cold in winter and mild in summer. Precipitation has high seasonal and interannual variation and may dier by an order of magnitude between geographically close locales, depending on slope, aspect and local climatic and orographic conditions. The region's hydrology is characterized by the accumulation of winter snow, spring snowmelt and autumnal base¯ows. During the 2±3-month`spring runo' period, rivers frequently discharge 470% of their annual water budget and have instantaneous discharges 10±100 times mean low¯ow.Complex weather patterns characterized by high spatial and temporal variability make predictions of future conditions tenuous. However, general patterns are identi®able; northern and western portions of the region are dominated by maritime weather patterns from the North Paci®c, central areas and eastern slopes are dominated by continental air masses and southern portions receive seasonally variable atmospheric circulation from the Paci®c and the Gulf of Mexico. Signi®cant interannual variations occur in these general patterns, possibly related to ENSO (El NinÄ o±Southern Oscillation) forcing.Changes in precipitation and temperature regimes or patterns have signi®cant potential eects on the distribution and abundance of plants and animals. For example, elevation of the timber-line is principally a function of temperature. Palaeolimnological investigations have shown signi®cant shifts in phyto-and zoo-plankton populations as alpine lakes shift between being above or below the timber-line. Likewise, streamside vegetation has a signi®cant eect on stream ecosystem structure and function. Changes in stream temperature regimes result in signi®cant changes in community composition as a consequence of bioenergetic factors. Stenothermic species could be extirpated as appropriate thermal criteria disappear. Warming temperatures may geographically isolate cole water stream ®shes in increasingly con®ned headwaters. The heat budgets of large lakes may be aected resulting in a change of state between dimictic and warm monomictic character. Uncertainties associated with prediction are increased by the planting of ®sh in historically ®shless, high mountain lakes and the introduction of non-native species of ®shes and invertebrates into often previously simple food-webs of large valley bottom lakes and streams. Many of the streams and rivers suer from the anthropogenic eects of abstraction and regulation. Likewise, many of the large lakes receive nutrient loads from a growing human population.We concluded that: (1) regional climate models are required to resolve adequately the complexities of the high gradient landscapes; (2) extensive wilderness preserves and national park lands, so prevalent in the Rocky Mountain Region, provide sensitive areas for dierentiation of anthropogenic eects from climate eects; and (3) future research should ...

StreamFlow 1.0: an extension to the spatially distributed snow model Alpine3D for hydrological modelling and deterministic stream temperature prediction

“…The forthcoming air temperature rise will lead to a modification of the riparian vegetation, which in turn will affect the stream ecosystem (Hauer et al, 1997). The higher stream temperatures will also have consequences on the cold-water fish species encountered in mountain streams, whose fry emergence date (Elliott and Elliott, 2010), growth rate (Hari et al, 2006) and death rate (Wehrly et al, 2007) are all mostly dependent on stream temperature.…”

“…The higher stream temperatures will also have consequences on the cold-water fish species encountered in mountain streams, whose fry emergence date (Elliott and Elliott, 2010), growth rate (Hari et al, 2006) and death rate (Wehrly et al, 2007) are all mostly dependent on stream temperature. Future increases in stream temperature are expected to result in a shift of the suitable habitat for such species to higher elevations, where dams and other physical barriers might limit their migration and result in a reduction of their habitat (Hauer et al, 1997;Hari et al, 2006). However, recent studies indicate that this habitat loss may be less important than was thought until now, since the high elevation gradients in mountainous areas imply only a small reduction of fish territory per degree increase in stream temperature (e.g.…”

Recent climate extremes alter alpine lake ecosystems

“…Although climate-driven aquatic changes have been both directly observed (4) and inferred (5,6) from data collected from polar sites, less is known about the climatic sensitivity of alpine lakes and streams (2,7,8). Climate warming and increased climatic variability are expected to alter snowpack, terrigenic inputs, ice-free season length, and summer water temperatures in unproductive high-elevation ecosystems, thereby affecting their biodiversity and functioning (7,(9)(10)(11)(12)(13).…”

Influence of wastewater on zooplankton communities in the Daugava River upstream and downstream of Daugavpils over the last 50 years

“…The changes mentioned above could be related to the consequences of climate change. Climate change resulting in warmer temperatures and a changed hydrological regime would alter the flux of water, heat and nutrients and thereby influence the seasonal dynamics of phytoplankton composition, responses of zooplankton, fish reproduction and overall bioproduction (Hauer et al, 1997). According to study results, the mean annual air temperature in Daugavpils has risen by about 1.3°C during the last 50 years.…”