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Communities of aspen (Populus tremuloides) are deteriorating throughout the western United States. Many aspen stands contain old-age or single-age trees and have not successfully regenerated for 80 years or longer. Moreover, many western aspen stands are being replaced by shade-tolerant conifers. These changes are usually attributed to the fact that aspen is a seral species whose decline is due to fire suppression. Kay believes that this view is incorrect. He points out that aspen is not seral as researchers typically believe, because the species does not grow from seed. Aspen seedlings are more common in the northern Canadian Rockies, and there may be windows of opportunity that allow seedling establishment at infrequent intervals of 200 or 400 years or even longer, but successful sexual reproduction of aspen is still very rare. This means that aspen clones found in the West today have survived thousands of years via vegetative regeneration. Research and experience have proven that aspen is extremely difficult to burn. Kay states that if aspen burned at frequent intervals in the past, as fire-frequency data and historical photos indicate it did, then the only logical conclusion is that those fires had to have been set by Native American, who used fire extensively to manage plant communities. Where native ungulates and domestic livestock have been excluded, aspen invariably produces multiaged stems, even where aspen is heavily invaded by conifers. Even when burned by wildfire or prescribed fire, aspen clones across the West fail to regenerate because of excessive browsing. Aspen is an excellent indicator of ecological integrity; therefore, maintaining and restoring aspen are important because those communities have exceedingly high biodiversity, second only to riparian areas on western ranges. Kay concludes that creating wilderness areas and parks and then allowing nature to take its course, often called hands-off or natural-regeneration management, will only consign aspen to extinction.