cmyles@milton.acs.washington.edu (Cathy Myles) (01/03/90)
My nephew is doing a project on 'snags' and has asked me to gather information for him. Snags are a home for many different types of birds, bugs, and other animals. At the same time they are a hazard to people walking around underneath them, especially loggers. The result of them being a hazard is that the British Columbia Worker's Compensation Board (injury insurance for workers) penalises loggers for not cutting them down. In the project my nephew wants to consider whether cutting the snags down is a good or bad idea. I would like mail about: what is done about them where you live, opinions on what should be done, what animals might be threatened by widespread snag removal, and anything else you can think of. Thanks in advance. Jamie
jimh@qtc.UUCP (Jim Hurst) (01/05/90)
In article <1220@milton.acs.washington.edu> you write: >I would like mail about: what is done >about them where you live, opinions on what should be done, what >animals might be threatened by widespread snag removal, and anything >else you can think of. > >Thanks in advance. Jamie Mail to your site bounced. Here's what I thought of. Snags are an important part of the undisturbed forest ecosystem. They provide a unique structural component of the forest, which is home to many different species of bugs and fungi with very narrow ecological niches. There are several species of birds and mammals dependent on snags for primary habitat, that is, habitat where they can reproduce, not just survive. Amongst the species that need cavities or standing snags are (this is from the appendix in Larry Harris' book listed below): saw-whet owl pygmy owl screech owl pileated woodpecker northern three-toed woodpecker hairy woodpecker tree swallow purple martin western bluebird mountain bluebird yellow-bellied sapsucker black-capped chickadee downy woodpecker chestnut-backed chickadee red-breasted nuthatch white-breasted nuthatch brown creeper Vaux's swift California myotis Yuma myotis little brown myotis fringed myotis (myotis ~= bat) long-legged myotis silver-haired bat big brown bat racoon marten fisher and of course spotted owl <------ that famous million dollar bird This list looks to me like there are degrees of need: there aren't many snags in my neighborhood, but lots of chickadees and several racoons. On the other hand, pileated woodpeckers, some owls, martens, fishers, and bats absolutely need snags to survive and reproduce. Snags aren't really an isolated feature, , they are part of the continuum of the forest. Conifers that sustain damage to the crown often begin a slow death from heart rot even as the lateral branches begin growing upward form an enclosure protected from the elements that is used by cavity nesting birds along with holes in dead trees. So by the time the tree dies (which can take decades or even centuries) and becomes a snag, it is home to a diverse community of birds, mammals, bugs, and sapprophytes. Snags indirectly protect the forest from insect damage by providing habitat for natural insect predators. Insect infestation tends to occur in isolated outbreaks, particularly in areas where the forest is stressed by drought, poor soil, fire damage, altitude, etc. In forests maintaining healthy populations of insect eating birds, woodpeckers and their friends home in on outbreaks early in their occurrence, usually preventing infestation from becoming large scale. On the other hand, snag can also provide an environment that allows the survival of large numbers of insects, and so can actually help facilitate insect infestation. What is done in our area? We litigate, wrangle, lobby and generally fight over snags and associated structurally diverse forests. The presence of snags is subsumed in the larger controversy over forest management and old growth in the Northwest. Preservation of the structural diversity of the forest, and its accompanying biological diversity has become the major issue on the agenda of the environmentalists in the region. They (we) are gradually gaining power and influence as the timber industry becomes a less dominant part of the regional economy. Traditional forest management has been based on clearcutting, and therefore on the removal of all snags, although leaving "wildlife" trees and snags has been practiced on occasion. Recent court decisions, combined with the Forest Service's stated intention of changing forestry practice with regard to ancient forest, indicate that snags and structural diversity in US forests will be handled more carefully in the future. Calls for a "new forestry" involving more snags and downed wood have begun to show results in the national forests of Oregon. The Blue River Ranger district of Willamette National Forest has done shown leadership in experimentation with timber harvest techniques that preserve structural divesity, including snags. Exactly how public forests will be managed after the timber compromise (aka the Appropriations Rider from Hell) of 1989 remains to be seen, but clearly more snags will be left in the future. What do I think should be done? I believe there are no simple generalizations as to the correct manner to manage the 10 million or so acres of federal forest in Oregon, although the hardline environmentalists in the Native Forest Council would tell you otherwise. So would the hardline timber industry folks, of course. (What did Newton say about equal and opposite forces?) An intelligent management program will combine a wide array of different techniques, and make an effort to apply those techniques best suited to the local conditions. That said, if I were king of the forest, I would require clearcuts no larger than some small threshold, say 10 acres. This threshold should probably actually be a function of the topography and local conditions. In silviculture speak, this becomes small selection cuts, rather than clearcuts. Leave all snags. Here's what Elliot Norse, past Public Policy Director of the Ecological Society of America, says about snags in his book: (note that this is in the context of the ancient forests of the Pacific Northwest. Your mileage may vary.) "Standing dead trees and fallen ones have different ecological roles. Snags offer sloughing slabs of bark, chimneylike cavities and vantages out of reach of ground-dwelling predators. They also attract birds whose droppings contain seeds of blackberries, salmonberries, thimbleberies, huckleberries, and other plants that colonize clearcuts and burns. Some plants, fungi, and invertebrates use both snags and logs, but most vertebrates use mainly one of the other. Snags are particularly important for birds, bats, and carnivorous mammals. Raptors (hawks and owls) use them for lookout and plucking posts; many birds use them for courtship display, nesting, feeding, and roosting sites and for thermal protection at night, during heavy rains, and in cold weather. Loose sheets of bark on snags are major breeding sites for brown creepers and for several kinds of bats. Cavities at the base of snags serve as dens for mammals as large as black bears, cavities higher up are nesting sites for 30-45 percent of Nortwest forest bird species and dens for squirrels, martens, and bobcats. In general, smaller snags can be used by some smaller species, but large snags are essential for larger species and some small ones too. Wood ducks, great horned owls, pileated woodpeckers, and fishers generally need snags more than 25 inches in diameter, but so do some smaller species, such as Vaux's swift. Height is also important; far more cavity-nesting species use tall snags than low-cut stumps. Although young forests often have more snags, the larger snags in ancient forests are far more valuble to cavity-dwelling wildlife. Most cavities in hard (younger) snags are excavated by woodpeckers preparing to nest. Chickadees and nuthatches also excavate cavities in soft (older) snags. When excavators move out, a wide variety of other birds and mammals can move in. By providing a crucial limiting resource, excavators function as keystone species, ones whose activites disproportionately influence other forest dwellers. Most excavators, in turn, depend on insects and fungi to soften snags. Wood boring beetles tunnel into trees soon after they die, providing entry for decomposing fungi. This allows woodpeckers and bears to shred the softened wood as they forage for beetle larvae. People who automatically consider insects and fungi to be pests might be supriessed to learn of their essential service to all cavity dwellers, from furbearing mammals and gamebirds to rare species such as spotted owls. As decomposition and shredding weaken a snag, it first loses its needles and twigs, then upper branches, bark, and the top of its trunk, then wood further down the bole. Some snags are firm when they fall, but many just disintegrate and collapse. Size affects their longevity, small ones decompose faster. In western Oregon, small Douglas fir snags characteristic of eighty year old stands fall within two decades. The large Douglas fir snags of ancient forests usually last more than 125 years. The species of snag affects longevity as well. Western redcedar and Douglas fir snags outlast western hemlocks and silver firs. So diameter, height, species, degree of decomposition, and numbers all affect the value of snags to forest wildlife. Entire trees need not die to provide essential vertial dead wood habitat for forest wildlife. The tops of many ancient conifers are dead, victims of wind, freezing, lightning strikes, bark beetles, or pathogenic fungi. Although dead tops - often the top 10%, sometimes even the top half - are difficult to see from the ground (and hence, are often missed in surveys), canopy dewllers use them in the same ways that they use snags. End quote. For more information, the following have some bearing on the general subject of snags: The Fragmented Forest Larry Harris University of Chicago Press 1984 The Redesigned Forest Chris Maser R & E Miles, San Pedro, CA 1988 Forest Primeval Chris Maser Sierra Club Books 1989 Ancient Forests of the Pacific Northwest Elliot Nourse Island Press, Covelo, CA/Washington DC 1989 Other recent books that might be of interest on other aspects of forests and forestry. Fragile Majesty Keith Ervin Sierra Club Books 1989 The Forest and the Trees Gordon Robinson Island Press 1988 Reforming the Forest Service Randall O'Toole Island Press 1988 Hope this helps, JimH