I am a plant ecologist interested in the great diversity of morphological and physiological features and functions that plants have evolved to live in their environments. One of the critical physiological functions of plants is the regulation of their water use. There are enormous differences among plants and among entire plant communities such as forests in how efficiently they use water. These differences in turn have practical implications for the retention and supply of clean water by different forest ecosystems. We recently discovered that in Hawaiian timber plantations, alien tree species that were introduced into Hawaii can use more than twice the amount of water to grow as native forests. This finding indicated that preserving native tropical forest has value beyond the conservation of the native trees, because water is expensive. Consequently, land management decisions can place ecosystems-and the people who depend on them-at increased risk of water shortages. We are conducting further research to understand why plants use different amounts of water that should eventually allow construction of water budgets over entire landscapes with complex land use mosaics, and from small-scale gardens to forests to large parks. In other projects, we are investigating the adaptation of plants to their environment, with a special focus on the evolution of plant groups that include endangered species. While our research is centered on pure science and discovery, this work has major environmental and economic implications, including applications toward the conservation of rare species and native forests.