Animal Jurisprudence

AFTER co-authoring a 2005 paper imagining “Re-wilding North America” with giant Bolson tortoises, camels, horses, cheetahs, elephants and lions, Harry Greene received a lot of hate mail. Corresponding ecologists hated the idea of deliberate transcontinental introductions of any kind.

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Seeing (less) red: Bark beetles and global warming

This post contributed by Jesse A. Logan, retired research entomologist living in Emigrant, Montana. The Greater Yellowstone Ecosystem (GYE) is an ecological reserve of regional, national and international significance. This collection of National Parks, National Forests, wildlife reserves and tribal lands is generally recognized as one of the last remaining large, nearly intact, ecosystems of the Earth’s northern temperate region. Climax whitebark pine (Pinus albicalus Engelman) forests comprise the majority of forested habitat above 2,750 meters and extend to the highest elevation as a crooked krumholtz growth form. By functioning as both a foundation and a keystone species, whitebark pine is an important ecological component of the GYE. Unfortunately, the foundation whitebark forests of the GYE are facing catastrophic collapse due to a combination of an introduced pathogen, unprecedented attack by a native bark beetle and climate change. Whitepine blister rust is a pathogen introduced near the turn of the past century, and its effect is to first compromise the reproductive capacity of the tree, eventually (requiring an average of twenty years in the GYE) leading to the tree’s death. On the other hand, attack by the native mountain pine beetle either immediately leads to the  tree’s deaths, or the tree successfully defends itself and repulses the attacking beetles. The seriousness of these threats to the integrity of high-elevation forests is indicated by the recent finding by the US Fish & Wildlife Service that whitebark meets the criteria for a threatened or endangered species; in addition, despite their risk of extinction, the FWS did not add whitebark to the endangered species list due to lack of sufficient funding. Under historic climate regimes, these high elevation forests were simply too cold for the mountain pine beetle (MPB) (Dendroctonus ponderosae) to thrive. Although, past MPB-caused whitebark pine mortality did occur during periods of unusually warm weather—for example, in the 1930s—these outbreaks were short-lived and limited in scale. With the publication of the first Interngovernmental Panel on Climate Change report in 1990, research on the potential for increased MPB activity in whitebark pine began to occur. Model predictions of high intensity MPB outbreaks began to be realized across the southern range of whitebark pine by the early 2000s. By 2005, USDA Forest Service Aerial Detection Survey (ADS) data showed significant MPB caused mortality across large areas of GYE whitebark pine. This mortality is first evident by large numbers of red trees (symptomatic of trees killed the previous summer), subsequently followed by vast areas of gray trees — the residual ghost forest — is shown in the photos above. In those photos of Hoyt Peak from Avalanche Peak near Sylvan Pass, Yellowstone National...

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Invasive tree disease disrupts pine/bird mutualism

Many trees with large seeds rely on vertebrate seed predators to disperse their seeds. The whitebark pine, a key subalpine species, has coevolved with the Clark’s nutcracker into a tight mutualism.  In their paper in the April Ecological Applications, Shawn McKinney, a post-doc at the University of Montana, and his colleagues studied a natural disruption to this mutualism: an invasive tree fungus. Clark’s nutcrackers feed on whitebark seeds throughout the summer. Beginning in late summer, the nutcrackers extract ripe whitebark pine seeds from pinecones and bury them in the ground for use as food during the winter and spring. Although the nutcrackers harvest and cache seeds of other pines, whitebark pines depend nearly exclusively on nutcrackers for seed dispersal. White pine blister rust, a disease caused by a tree pathogen that kills cone-bearing branches, has been spreading through the subalpine forests and now occurs in almost all whitebark pine populations. According to the researchers, mortality from blister rust reaches 90 percent or higher in some populations in the northern Rocky Mountains. For the trees, this disease can spell disaster: When whitebark pine seeds are scarce, the nutcrackers often leave subalpine forests in search of food at lower altitudes. Decimated by disease and left without dispersers to spread what few seeds they produce, whietbark pines can dwindle rapidly. McKinney and his colleagues quantified forest conditions and ecological interactions between nutcrackers and whitebark pines in three Rocky Mountain ecosystems that differed in levels of rust infection and mortality. They estimated that within each hectare, a threshold level of 1000 pinecones, or more than a 5-meter square area of trees, is needed for a high likelihood of seed dispersal by nutcrackers. The researchers say that their estimates can be used by forest managers to assess when and where to plant new stands of whitebark pines to encourage nutcrackers to stick around. They say the estimates will be especially useful in Montana, where pinecone production and tree density fell below threshold levels. McKinney, S., Fiedler, C., & Tomback, D. (2009). Invasive pathogen threatens bird–pine mutualism: implications for sustaining a high-elevation ecosystem Ecological Applications, 19 (3), 597-607 DOI:...

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