An experiment in >1000 river and riparian sites found spatial patterns and controls of carbon processing at the global scale.

1. About half of the world's tropical peatlands occur in Southeast (SE) Asia, where they serve as a major carbon (C) sink. Nearly 80% of natural peatlands in this region have been deforested and drained, with the majority under plantations and agriculture. This conversion increases peat oxidation which contributes to rapid C loss to the atmosphere as greenhouse gas emissions and increases their vulnerability to fires which generate regional smoke haze that has severe impacts on human health. Attempts at restoring these systems to mitigate environmental problems have had limited success.2. We review the current understanding of intact and degraded peatlands in SE Asia to help develop a way forward in restoring these ecosystems. As such, we critically examine them in terms of their biodiversity, C storage, hydrology and nutrients, paying attention to both above-ground and below-ground subsystems.3. We then propose an approach for better management and restoration of degraded peatlands that involves explicit consideration of multiple interacting ecological factors and the involvement of local communities who rely on converted peatlands for their livelihood. 4. We make the case that as processes leading to peatland development involve modification of both above-ground and below-ground subsystems, an integrated approach that explicitly recognizes both subsystems and their interactions is key to successful tropical peatland management and restoration. Synthesis and applications.Gaining a better understanding of not just carbon stores and their changes during peat degradation, but also an in-depth understanding of the biota, nutrient dynamics, hydrology and biotic and abiotic feedbacks, is key to developing better solutions for the management and restoration of peatlands in Southeast Asia. Through the application of science-and nature-based solutions | 1371

Tropical peatlands store around one-sixth of the global peatland carbon pool (105gigatonnes), equivalent to 30% of the carbon held in rainforest vegetation. Deforestation, drainage, fire and conversion to agricultural land threaten these ecosystems and their role in carbon sequestration. In this Review, we discuss the biogeochemistry of tropical peatlands and the impacts of ongoing anthropogenic modifications. Extensive peatlands are found in Southeast Asia, the Congo Basin and Amazonia, but their total global area remains unknown owing to inadequate data. Anthropogenic transformations result in high carbon loss and reduced carbon storage, increased greenhouse gas emissions, loss of hydrological integrity and peat subsidence accompanied by an enhanced risk of flooding. Moreover, the resulting nutrient storage and cycling changes necessitate fertilizer inputs to sustain crop production, further disturbing the ecosystem and increasing greenhouse gas emissions. Under a warming climate, these impacts are likely to intensify, with both disturbed and intact peat swamps at risk of losing 20% of current carbon stocks by 2100. Improved measurement and observation of carbon pools and fluxes, along with process-based biogeochemical knowledge, is needed to support management strategies, protect tropical peatland carbon stocks and mitigate greenhouse gas emissions.Peatlands hold the largest terrestrial pool of organic carbon (C) in the biosphere, storing 600-650gigatonnes (Gt) (refs1-3 ). They also play a part in the cycling of nutrients and the delivery of other ecosystem services, including regulation of the water supply and biodiversity support. Most of the global peatland C stock is in the high northern latitudes (Table 1) and is largely remote from human influence. However, approximately 16% of peatland C (around 105Gt)1,2 is held in C-dense tropical peatlands, some of which are close to large and growing human populations4 . The utilization of peatlands for forestry, agriculture and other purposes has converted them from a longterm C sink into an intense source of greenhouse gas emissions, contributing about 5% of global anthropogenic emissions5 . Mid-latitude and tropical peatlands supply the majority of this total6,7 and are increasingly acknowledged as critical in the global C cycle and in efforts to combat climate change8-11. There is growing understanding and recognition of tropical peatland extent and the consequences of human and climate-driven disturbances, particularly in loss of stored C and enhanced greenhouse gas emissions11. Anthropogenic impacts on tropical peatlands span a gradient from minor vegetation modification through to vegetation removal, alteration of hydrology by drainage, and changes in peat physical and biogeochemical properties resulting from land-use conversion and fire. These alterations have been extensive in Southeast Asia, but peatlands in other tropical regions are increasingly exposed to human and climate impacts as a result of socioeconomic development, warming temperatures and altere...

Networks of engineered waterways are critical in meeting the growing water demands in megacities. To capture and treat rainwater in an energy-efficient manner, approaches can be developed for such networks that use ecological services from microbial communities. Traditionally, engineered waterways were regarded as homogeneous systems with little responsiveness of ecological communities and ensuing processes. This study provides ecogenomics-derived key information to explain the complexity of urban aquatic ecosystems in well-managed watersheds with densely interspersed land-use patterns. Overall, sedimentary microbial communities had higher richness and evenness compared to the suspended communities in water phase. On the basis of PERMANOVA analysis, variation in structure and functions of microbial communities over space within same land-use type was not significant. In contrast, this difference was significant between different land-use types, which had similar chemical profiles. Of the 36 environmental parameters from spatial analysis, only three metals, namely potassium, copper and aluminum significantly explained between 7% and 11% of the variation in taxa and functions, based on distance-based linear models (DistLM). The ecogenomics approach adopted here allows the identification of key drivers of microbial communities and their functions at watershed-scale. These findings can be used to enhance microbial services, which are critical to develop ecologically friendly waterways in rapidly urbanizing environments.

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