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McCarty, John P. 2001."Ecological Consequences of Recent Climate Change."

Conservation Biology Vol.15, No. 2: 320-331

RELEVANT TO: GLOBAL WARMING

DECLINING SPECIES

FOREST VEGETATION

LIVESTOCK GRAZING

GRASSLANDS/SHRUBLANDS

FIRE MANAGEMENT

INVASIVE SPECIES

DESCRIPTION OF DOCUMENT

This document reviews the rapidly accumulating, direct documentation of changes in species and ecosystems linked to global warming. A growing number of studies suggest that global climate change may not be just a conservation problem for the future but may in fact be a current threat to species and ecosystems. This document looks at the role of climate in the ecology of species and then, more specifically, looks at recent ecological changes and the link to climate change.

It outlines studies that document changes in phenology (timing of breeding), changes in geographic range, community and ecosystem-level changes (such as precipitation and temperature), productivity of native grasses and species composition changes, and the risk of extinction caused by climate change. It closes with a review of the implications for conservation and resource management.

MAJOR FINDINGS

1. Extensive disruptions of most ecological communities are likely under generally accepted scenarios. The earth's climate has warmed 0.3 to 0.6 degrees C over the last 100 years. Although the average increase of 0.5 degrees C is significant for many physiological and ecological systems, this single value understates the magnitude of the changes to which species have been exposed. Temperature changes vary geographically and tend to be greatest during the coldest months.
2. Climate has far-reaching effects on species and ecosystems. The direct effects of temperature on the physiology of organisms are well documented:

• The sex of developing turtle embryos is determined by environmental temperature; painted turtle (Chrysemys picta) eggs raised under warmer conditions produce female offspring, whereas males are produced under cooler conditions. Under some climate-change scenarios, Janzen (1994) indicates that local extinctions may occur in the near future as a result of the skewed sex ratio.
• Precipitation levels have direct effects on species. Distribution of ponderosa pine forest (Pinus ponderosa) and pinyon-juniper woodland (Pinus edulis and Juniperus monosperma) in New Mexico are sensitive to moisture levels that vary with elevation (Allen and Breshears 1998). Data from aerial photos taken between 1935 and 1975 show a rapid change (2 km in <5 years) in the distributions of these two communities in response to a regional drought.
• Climate has indirect effects for many species through the sensitivity of habitat or food supply to temperature and precipitation. Increases in winter snow depth on Isle Royale associated with the North Atlantic oscillation result in grey wolves (Canis lupus) hunting in larger packs (Post et al. 1999). Likewise, warming climate may allow northward expansion of red fox (Vulpes vulpes), which outcompetes arctic fox (Vulpes lagopus) (Hersteinsson and MacDonald 1992).

1. Climatic warming during the past century may have significant effects on the population and reproductive biology of organisms:

• Recent population dynamics of dippers (Cinclus cinclus) in southern Norway have been heavily influenced by climate, especially a trend toward warmer winters which appears to allow easier access to foraging streams and subsequent increases in population size (Sæther et al. 2000).
• In pied flycatchers (Ficedula hypoleuca) in Germany, both clutch size and the number of surviving offspring were higher in warmer springs (Winkel and Hudde 1997). In contrast, the average clutch size of arctic-breeding geese declined during the warming period from 1951 to 1986 (MacInnes et al. 1990).

1. Recent climate change is linked to both increases and declines in population size. Rapid declines in population are of direct concern. Increases in valued species (Dennis and Shreeve 1991) will likely be offset by population increases in groups such as invasive exotics (Bergstrom and Chown 1999, etc.), disease vectors (Lindgren et al 2000), and agricultural pests (Cammell and Knight 1992, etc.). Negative effects of further increases in already abundant, aggressive species will likely overwhelm any benefits of climate change.
2. A number of studies have documented the long-term changes in phenology which may be caused by global change:

• In the United Kingdom, bird nesting data collected for 60 years indicates that 78 percent of 65 species examined started breeding earlier as measured from 1971 to 1995 (Crick et al. 1997).
• Great tits (Parus major) in the U.K. and Germany now breed up to 10 days earlier than in 1970, when the region's warming trend began (Winkel and Huddle 1997, etc.). Mexican jays (Aphelocoma ultramarina) in Arizona started nesting 10 days earlier between 1971 and 1997 (Brown et al. 1999).
• One of the best examples of phenological change in a single species is the advance in breeding date in tree swallows (Tachycineta bicolor). Dunn and Winkler (1999) used nest records collected across much of the tree swallow's range to document a shift in breeding date of 5-9 days earlier in the season between 1959 and 1991. This example emphasizes that phonological changes within a species influenced by local conditions can produce patterns at continental scales.
• Long-term data on the timing of bird migration is available. In New York, records of spring arrival for 76 species of migrating landbirds dating back to 1903, indicate that over a 90-year period, 39 species arrived significantly earlier, 35 species showed no significant changes, and only 2 species arrived later in the spring (Oglesby and Smith 1995).
• Records of British butterfly species indicate that timing of first observation has changed along with climate (Sparks and Carey 1995, etc.) Analysis in Great Britain shows that, over 25 years, the flight period of five species of aphids has become 3-6 days earlier (Fleming and Tatchell 1995).
• Breeding of amphibians is also starting earlier in the spring. Based on 17 years of data on frogs and newts in the U.K., Beebee (1995) showed that migration of breeding ponds and spawning dates has occurred 2-7 weeks earlier in recent years.
• Oglesby and Smith (1995) found that flowering dates of spring wildflowers in New York showed a directional trend consistent with climate warming during this century: in 6 of 15 species with available data, blooming had advanced at a rate of 20 days per 50 years, and no species flowered significantly later.

1. Changes in phenology will likely disrupt many species and interactions. Many of the results presented above indicate that many species have some capacity to respond rapidly to climate changes by altering the timing of life-history events. But it is not safe to assume that this will be a general pattern. A shift in phenology may disrupt important correlations with other ecological factors. Species that regularly move between habitats may need to adjust to climate changes that are occurring at different rates in different areas, such as between high and low elevations (Inouye et al. 1995). Plant-animal interactions such as pollination and seed dispersal depend on synchrony between species. Specific species depend on the appearance of specific foods at critical times (Fritter et al. 1995, etc.).

• In the Netherlands, warmer springs have resulted in a mismatch between the time of peak availability of insects and the peak food demands of nestling great tits (Visser et al. 1998). In this population, the birds have not begun breeding earlier, even though consistent warming of 23 years has resulted in the peak availability of the insects they eat occurring 9 days earlier. Disruptions such as this will reduce the availability of threatened species to cope with other environmental stresses.

1. Change in geographic range for many species is determined by climate. Recent northward movements of species' range boundaries consistent with climate warming have been observed in birds (Thomas and Lennon 1999), mammals (Payette, 1987, etc.), and butterflies (Dennis 1993, etc.).

• Northward expansion of bird species in North America and Europe have been observed over the past 50 years (Kalela 1949, etc.).Thomas and Lennon (1999) compared breeding ranges of birds in 1968-1972 to ranges in 1988-1991. Of 59 species occupying southern Great Britain, the northern boundary of their ranges shifted an average of 19 km to the north (including those species showing no change in the southern boundary of their ranges). This comparison shows that the northern and southern range boundaries of species are not equally sensitive to climate change.
• Parmesan et al. (1999) examined changes in the northern range boundaries of 52 species of European butterflies over the past 30 to 100 years. The northern boundaries of geographic ranges showed northward shifts in 34 species, southward shifts in 1 species, and no change in the remaining 17 species. The southern boundaries of species' ranges were more stable over time. Although explanations not linked to climate cannot be ruled out, Parmesan et al. (1999) assert that habitat loss has actually been higher in the north than the south, indicating that in this case habitat loss is not driving changes in species' ranges.
• In mountains, climate changes more rapidly with elevation (about 1 degree C per 160 m) than is does with latitude (about 1 degree C per 150 km), so rapid changes in montane communities are expected as climate changes. Grabherr et al. (1994) surveyed montane plants on 26 mountain summits in the Swiss Alps and compared species distributions to historical records. The relationship of species richness to elevation showed a pronounced shift to higher elevations over the past 49-90 years, consistent with the effects of warming. For 9 species with more detailed records, the rate of upward shirt was estimated to be 1-4 m per decade. Dieback of montane trees (Hamburg and Cogbill 1988, etc.) are consistent with the effects of warming climate. Parmesan (1996) documented an upward shift of 124 m in the distribution of Edith's checkerspot butterfly, primarily in the Sierra Nevada mountains.

1. Changes in precipitation and temperature result in community-and ecosystem-level changes:

• Changes in precipitation patterns in the arid regions of the southwestern U.S. have resulted in a shift at some sites from arid grassland to desert shrublands, accompanied by the local extinction of several formerly abundant species of animals (Brown et al. 1997).
• In the shortgrass steppe of northeast Colorado, average temperatures have risen 1.3 degrees C since 1979, largely because of a rapid increase in nighttime temperatures (Alward et al. 1999). Measurements of the annual net primary productivity of the dominant native grass in this habitat, Bouteloua gracilis, reveal a significant decline over this period. Bouteloua gracilis accounted for 90% of the groundcover in this ecosystem, and the magnitude of the decline in productivity suggests that major disruptions in both ecosystem structure and functioning could result from further warming (Allward et al. 1999). Exotic species responded favorably to warming, raising the possibility of further invasions of the community by non-native weeds.

1. Climate change can contribute to future extinctions: Ongoing climate change is an additional source of stress for species already threatened by local and global environmental change.

• Recent climate change may be directly responsible for the extinction of the golden toad (Bufo periglenes) from the Costa Rican cloud forest (Pounds and Crump 1994, etc.). Global warming may also be indirectly linked to amphibian declines resulting from UV radiation (Blaustein et al. 1995).
• Climate acts locally, and its effects will be most apparent on the level of populations and metapopulations. Shifts in a species' range under climate change will occur in part as a result of an increase in the probability of more southerly populations going extinct. Parmesan (1996) resurveyed 151 sites that had once hosted populations of Edith's checkerspot butterfly. Population extinction rates were higher in the southern part of the species' historic range and at low elevations.
• The recognition of the role of local extinctions and the importance of metapopulation dynamics in range shifts in response to climate change are especially relevant given the local focus of many conservation efforts. Loss of local, familiar species and species serving important ecological roles may become the rule. This is a problem for conservation biology because stakeholders value local species and because lost species are most likely to be replaced by exotic, invasive species (Dukes and Mooney 1999).

1. The implications of climate change for conservation and resource management are clear. The studies reviewed in this paper emphasize that conservation scientists need to look at climate change as a current, not just a future, threat to species. Although a causal link to climate cannot yet be rigorously demonstrated, the consistent patterns indicate that the prudent course for conservation is to take these changes seriously. The available evidence indicates that changes in the Earth's climate will likely continue and even accelerate over the next 50-100 years (IPCC 1996).

• the rate at which species' boundaries can change is of key importance to understanding how species will respond to climate change. The ability of butterflies to move 35-140 km during a period when isotherms shifted 120 km shows that many species are capable of matching the recent rate of climate change (Parmesan et al. 1999), but it does not preclude faster change.
• The overall picture that emerges is that conservation biologists need to add another source to the long list of stressors that may be causing population and species decline. These results add to the urgency to consider climate change when planning for conservation and to consider the interactions between climate change and other stressors such as habitat fragmentation (Markham 1996, etc.).

QUESTIONS THIS RAISES FOR THE THREE FORESTS

• What implication does a predicted increase of 0.3 to 0.6 degrees C during the life of the Forest Plans (10-20 years) have on native plant and animal species of the Three Forests?
• Have changes in the distribution of any forest, shrubland and grassland vegetation and/or species' ranges been searched for and/or documented on the Three Forests during the life of the current forest plans?
• What listed, sensitive and species of concern have been or may be affected by changes in the climate of the Three Forests? What is the effect of continued and possibly increased rates of climate change as an additive factor on existing stressors for these species on the Three Forests?
• What species may be negatively impacted by a northward shift in range of 35-140 km? Which species would likely "run out" of habitat on the Three Forests?

FOREST MANAGEMENT SIGNIFICANCE

Proactively address the issue of climate change and potential effects at the local (e.g. Forest) level.

1. Establish 10 species for which phenological trends (e.g., flowering, nesting, migration arrival/departure) will be tracked. These species should include flowering plants, neotropical migrants, butterflies, and amphibians. Develop a monitoring scheme for these species that will allow for systematic and redundant tracking of phonological trends by interested publics; all collected information would be provided to the Forests.

1. Identify species for which climate change may result in habitat loss or change due to increased temperatures and/or changes in precipitation (e.g. loss of microclimate, changes to food base, loss of or changes to vegetation, increase in non-native species, etc.). Identified species should be included as management indicator species within the Three Forests. These species should include American pika (Ochotona princeps). Western toad (Bufo boreas), American marten (Martes americana) [Manti-La Sal], and wolverine (Gulo gulo).

1. Proactively provide for greater buffering of native species through:

• retention of instream flow;
• attention to water holding capacity in meadows (i.e., avoidance of compaction);
• of bare soil conditions;
• prevention of the conditions that favor the introduction, establishment, and spread of invasive species;
• retention of natural forest overstory and grass and forb understory for shade
• redundancy in size and distribution of populations of rare and sensitive species
• avoidance of activities that result in unnaturally dense forest growth which favors fire

1. Coordinate with surrounding public land agencies (e.g., BLM, National Park Service, Utah State Parks and Recreation) and researchers to protect the habitat of species that are affected by climate change (e.g., declining, moving northward).