A recent outbreak of a deadly fish parasite on the Yellowstone River may have seemed unremarkable. But a new wave of research shows the episode was likely linked to the cumulative impact of human activities that essentially weakened the Yellowstone’s “immune system.”
Last August, the Yellowstone made national headlines when a parasite killed thousands of fish, mostly whitefish. Fear of spreading the parasite to other waterways forced Montana officials to close the river to fishermen, rafters, and boaters. At the height of summer, the stunningly scenic, trout-rich river was eerily deserted. Fishing re-opened in the fall, but the parasite has been found in other Montana waterways.
That a non-native parasite somehow got into a river may seem like an unremarkable occurrence. But a new, expansive model of gravel-bed river systems in mountainous areas, such as the Yellowstone, depicts a more complex scenario in which a host of human activities combine to degrade river systems and render them more vulnerable to destructive outside influences such as parasites. This body of research — 40 years in the making, but much of it summed up in a recent paper — rewrites the understanding of the ecological dynamics of these rivers. And it casts a harsh light on human river valley activities such as homebuilding, dam construction, irrigation, and channelization that may be slowly choking highly dynamic river systems — and the biodiversity that depends on them — to death.