Mountainous regions offer not only essential habitat and resources, including water, to the earth's more than 6 billion inhabitants, but also insights into how the global human habitat works, how it is being changed at the moment as global climates are disrupted, and how the disruption may lead to global biotic and economic impoverishment. At least 600 million of the earth's more than 6 billion...

We describe todolists (top-down skiplists), a variant of skiplists (Pugh 1990) that can execute searches using at most log2−εn +O(1) binary comparisons per search and that have amortized update timeO(ε−1 logn). A variant of todolists, called working-todolists, can execute a search for any element x using log2−εw(x)+ o(logw(x)) binary comparisons and have amortized search time O(ε−1 logw(w)). He...