It is this unique interplay of water, sediment, and vegetation, both prehistoric and contemporary, unregulated for the majority of it's existence and modified in striking ways during the last century, that lures geographers, hydrologists, and biologists to this incredible living laboratory. In September 2001, the Journal of Arid Environments (Volume 49) dedicated a special issue on the Delta. Here, the findings of some of the scientists that have been drawn to this largely unknown area are presented. Hopefully, it serves to whet the appetite of a new generation of explorers and scientists eager to help us understand the many aspects of the Colorado River Delta that have yet to be explained

    The papers found in JAE, volume 49, are organized into four sections: Reviews, Hydrology and Water Quality, Vegetation and Wildlife Dynamics and Policy Issues. There are two review papers: the first describes the major ecozones in the delta today and identifiies the water sources that support them (Glenn et al, 2001), and the second reviews the critical effect of flow regime on vegetation along desert rivers (Stromberg, 2001). The Hydrology and Water Quality papers describe a water balance study of the delta during flood and non-flood years (Cohen et al., 2001), while Glenn et al. (2001) document the return of native cottonwood (Populus fremontii) and willow (Salix gooddingii) trees to the riparian corridor in response to pulse floods, and estimate the amount of water needed to support this ecozone. Garcia-Hernandez (2001) and King et al. (2001) report on levels of toxic substances in the sediments and biota of the delta ecozones, and compare their results to those obtained on upstream river stretches in the US.

    The widespread replacement of native trees by the exotic shrub, salt cedar (Tamarisk ramosissima), and the ecophysiological conditions that can help reestablish native trees, is explored in three papers in the Vegetation and Wildlife Dynamics sections, addressing the effects of salinity and water deficit (Vandersandae et al., 2001), siltation (Levine and Stromberg, 2001), and nuturients (Marler et al., 2001) on seedling establishment under greenhouse conditions. The distribution of two endangered bird species in the delta is described in Garcia-Hernandez et al. (2001) and Hinojosa-Huerta et al. (2001).

    Perceptions of the river by stakeholders on both sides of the border, especially by residents of the delta, and prospects for conserving and enhancing the delta habitats are explored in two papers in the Policy Section. Varady et al.(2001) summarize the points of view expressed at the 'to the Sea of Cortez' symposium, while Pitt (2001) addresses the big question in "Can the Delta Be Restored?." The policy papers both emphasize the need for further research to understand the Delta ecosystems. Hence, this volume should be viewed as a starting point rather than a source of answers for all the questions about the Delta and its connection to the larger ecoregion.