Mercury has contaminated rivers worldwide, with health consequences for aquatic organisms and humans who consume them. Researchers have focused on aquatic birds as sentinels for mercury. However, trophic transfer between adjacent ecosystems could lead to the export of aquatic mercury to terrestrial habitats. Along a mercury-contaminated river in Virginia, United States, terrestrial birds had significantly elevated levels of mercury in their blood, similar to their aquatic-feeding counterparts. Diet analysis revealed that spiders delivered much of the dietary mercury. We conclude that aquatic mercury pollution can move into terrestrial habitats, where it biomagnifies to levels in songbirds that may cause adverse effects. Rivers contaminated with mercury may pose a threat to the many bird species that feed on predatory invertebrates in adjacent riparian habitats.
Spatial optimization approaches that were originally developed to help conservation organizations determine protection decisions over small spatial scales are now used to inform global or continental scale priority setting. However, the different decision contexts involved in large‐scale resource allocation need to be considered. We present a continuous optimization approach in which a decision‐maker allocates funding to regional offices. Local decision‐makers then use these funds to implement habitat protection efforts with varying effectiveness when evaluated in terms of the funder's goals. We illustrate this continuous formulation by examining the relative priority that should be given to different counties in the coterminous United States when acquiring land to establish new protected areas. If weighting all species equally, counties in the southwest United States, where large areas can be bought cheaply, are priorities for protection. If focusing only on species of conservation concern, priorities shift to locations rich in such species, particularly near expanding exurban areas facing high rates of future habitat conversion (e.g., south‐central Texas). Priorities for protection are sensitive to what is assumed about local ecological and decision‐making processes. For example, decision‐makers who doubt the efficacy of local land protection efforts should focus on a few key areas, while optimistic decision‐makers should disperse funding more widely. Efforts to inform large‐scale conservation priorities should reflect better the types of choice that decision‐makers actually face when working over these scales. They also need to report the sensitivity of recommended priorities to what are often unstated assumptions about local processes affecting conservation outcomes.
Marine protected areas (MPAs) are increasingly integrated into fishery management for coastal systems. Size and spacing rules (SSRs) have been proposed as simple MPA design guidelines, especially in regions where population connectivity data are limited.
We assessed whether SSRs allow managers to design effective MPA networks under spatiotemporally varying dispersal patterns using a spatially realistic population model parameterized for a commercially‐exploited fish species on the Great Barrier Reef.
SSRs are used to design MPA networks, and population simulations are used to measure the mean and variance of the resulting population size and fishery catch.
We show that SSR performance is contingent on the extent of the MPA network, and whether species’ connectivity data can be used to target areas for protection. For example, in the absence of connectivity data, a “many small” MPAs rule provides the least variable management outcome.
Synthesis and applications. We demonstrate that the performance and usefulness of size and spacing rules (SSRs) as guidelines for marine protected areas (MPAs) depend on the level of knowledge about larval dispersal, as well as the level of current exploitation in the fishery. These context‐dependent results offer particularly relevant guidance to future MPA design projects in regions with limited connectivity data.
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