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Cold-water species in temperate lakes face two simultaneous climate-driven ecosystem changes: warming and browning of their waters. Browning refers to reduced transparency arising from increased dissolved organic carbon (DOC), which absorbs solar energy near the surface. It is unclear whether the net effect is mitigation or amplification of climate warming impacts on suitable oxythermal habitat (<20 °C, >5 mgO/L) for cold-loving species because browning expands the vertical distribution of both cool water and oxygen depletion. We analyzed long-term trends and high-frequency sensor data from browning lakes in New York’s Adirondack region to assess the contemporary status of summertime habitat for lacustrine brook trout. Across two decades, surface temperatures increased twice as fast and bottom dissolved oxygen declined >180% faster than average trends for temperate lakes. We identify four lake categories based on oxythermal habitat metrics: constrained, squeezed, overheated, and buffered. In most of our study lakes, trout face either seasonal loss (7 of 15) or dramatic restriction (12 to 21% of the water column; 5 of 15) of suitable habitat. These sobering statistics reflect rapid upward expansion of oxygen depletion in lakes with moderate or high DOC relative to compression of heat penetration. Only in very clear lakes has browning potentially mitigated climate warming. Applying our findings to extensive survey data suggests that decades of browning have reduced oxythermal refugia in most Adirondack lakes. We conclude that joint warming and browning may preclude self-sustaining cold-water fisheries in many temperate lakes; hence, oxythermal categorization is essential to guide triage strategies and management interventions. 

Abstract Sustaining the organisms, ecosystems and processes that underpin human wellbeing is necessary to achieve sustainable development. Here we define critical natural assets as the natural and semi-natural ecosystems that provide 90% of the total current magnitude of 14 types of nature’s contributions to people (NCP), and we map the global locations of these critical natural assets at 2 km resolution. Critical natural assets for maintaining local-scale NCP (12 of the 14 NCP) account for 30% of total global land area and 24% of national territorial waters, while 44% of land area is required to also maintain two global-scale NCP (carbon storage and moisture recycling). These areas overlap substantially with cultural diversity (areas containing 96% of global languages) and biodiversity (covering area requirements for 73% of birds and 66% of mammals). At least 87% of the world’s population live in the areas benefitting from critical natural assets for local-scale NCP, while only 16% live on the lands containing these assets. Many of the NCP mapped here are left out of international agreements focused on conserving species or mitigating climate change, yet this analysis shows that explicitly prioritizing critical natural assets and the NCP they provide could simultaneously advance development, climate and conservation goals. 

Computational advances reveal opportunities for more sustainable hydropower development in large transboundary river basins. 

Rivers and streams contribute to global carbon cycling by decomposing immense quantities of terrestrial plant matter. However, decomposition rates are highly variable and large-scale patterns and drivers of this process remain poorly understood. Using a cellulose-based assay to reflect the primary constituent of plant detritus, we generated a predictive model (81% variance explained) for cellulose decomposition rates across 514 globally distributed streams. A large number of variables were important for predicting decomposition, highlighting the complexity of this process at the global scale. Predicted cellulose decomposition rates, when combined with genus-level litter quality attributes, explain published leaf litter decomposition rates with high accuracy (70% variance explained). Our global map provides estimates of rates across vast understudied areas of Earth and reveals rapid decomposition across continental-scale areas dominated by human activities. 

River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.