Mangroves are one of the most carbon‐dense forests on the Earth and have been highlighted as key ecosystems for climate change mitigation and adaptation. Hundreds of studies have investigated how ...mangroves fix, transform, store, and export carbon. Here, we review and synthesize the previously known and emerging carbon pathways in mangroves, including gains (woody biomass accumulation, deadwood accumulation, soil carbon sequestration, root and litterfall production), transformations (food web transfer through herbivory, decomposition), and losses (respiration as CO2 and CH4, litterfall export, particulate and dissolved carbon export). We then review the technologies available to measure carbon fluxes in mangroves, their potential, and their limitations. We also synthesize and compare mangrove net ecosystem productivity (NEP) with terrestrial forests. Finally, we update global estimates of carbon fluxes with the most current values of fluxes and global mangrove area. We found that the contributions of recently investigated fluxes, such as soil respiration as CH4, are minor (<1 Tg C year−1), while the contributions of deadwood accumulation, herbivory, and lateral export are significant (>35 Tg C year−1). Dissolved inorganic carbon exports are an order of magnitude higher than the other processes investigated and were highly variable, highlighting the need for further studies. Gross primary productivity (GPP) and ecosystem respiration (ER) per area of mangroves were within the same order of magnitude as terrestrial forests. However, ER/GPP was lower in mangroves, explaining their higher carbon sequestration. We estimate the global mean mangrove NEP of 109.1 Tg C year−1 (7.4 Mg C ha−1 year−1) or through a budget balance, accounting for lateral losses, a global mean of 66.6 Tg C year−1 (4.5 Mg C ha−1 year−1). Overall, mangroves are highly productive, and despite losses due to respiration and tidal exchange, they are significant carbon sinks.
Estuaries are highly productive habitats that support fisheries production. However, the importance of mangrove carbon to estuarine consumers can differ considerably among systems. In this study, we ...used stable isotopes (δ
13
C, δ
15
N) to investigate the importance of mangrove carbon as an energy source to estuarine consumers in the Atrato River Delta, Colombia, an area where fringing mangroves dominate the coastline and where other productive coastal habitats that may otherwise support the food web are absent. Basal resources and consumers were collected from mangrove and nearshore habitats during the rainy season. Results revealed a food web with a maximum length of 4.6 trophic positions. Bayesian mixing models indicated that most consumers used a mixture of basal sources, which suggests intertwined energetic pathways. However, mixing models also indicated that some species relied more heavily on some basal sources than others and revealed trophic pathways (food chains). Mangrove carbon directly supported herbivorous crabs (Sesarmidae) and indirectly supported planktivorous fish (Engraulidae) and piscivorous fish. Mangrove carbon also contributed significantly to the diet of 2 of the most common fish species in the local artisanal fishery:
Centropomus undecimalis
(mean: 46%; credibility interval CI: 1-80%) and
C. pectinatus
(mean: 33%; CI: 1-78%). Our findings highlight that mangrove carbon can be an important food source in areas without other productive coastal habitats and can play an important role in sustaining the production of fisheries.
Intermittent rivers and ephemeral streams (IRES) may represent over half the global stream network, but their contribution to respiration and carbon dioxide (CO2) emissions is largely undetermined. ...In particular, little is known about the variability and drivers of respiration in IRES sediments upon rewetting, which could result in large pulses of CO2. We present a global study examining sediments from 200 dry IRES reaches spanning multiple biomes. Results from standardized assays show that mean respiration increased 32‐fold to 66‐fold upon sediment rewetting. Structural equation modeling indicates that this response was driven by sediment texture and organic matter quantity and quality, which, in turn, were influenced by climate, land use, and riparian plant cover. Our estimates suggest that respiration pulses resulting from rewetting of IRES sediments could contribute significantly to annual CO2 emissions from the global stream network, with a single respiration pulse potentially increasing emission by 0.2–0.7%. As the spatial and temporal extent of IRES increases globally, our results highlight the importance of recognizing the influence of wetting‐drying cycles on respiration and CO2 emissions in stream networks.
Key Points
Sediment respiration in intermittent rivers and ephemeral streams increases substantially in response to rewetting
Respiration pulses are driven by sediment properties, which, in turn, are influenced by climate and catchment characteristics
Effects of wetting‐drying cycles on respiration and CO2 emissions in stream networks need consideration in upscaling and modeling efforts
By definition the HELP approach involves the active participation of individuals from a wide range of disciplines and backgrounds, including representatives of industry, academics, natural resource ...managers, and local officials and community leaders. While there is considerable enthusiasm and support for the integrated HELP approach, a central problem for all HELP basins is how to effectively engage individuals and groups with few, if any financial resources. In the Luquillo HELP project we have managed this issue by focusing our efforts on holding small, public meetings and workshops with technocrats and managers who are engaged in local water resource management. To date several forums have been organised, including: technical meetings with the directors of natural resource agencies; presentations and panel discussions at the meetings of local professional societies, including the societies of Civil Engineers and Architects, the Commonwealth Association of Tourism, the Association of Builders and Developers, and the Puerto Rican Association of Lawyers. During these forums HELP specialists gave presentations and led discussions on how integrated watershed management can help resolve local problems. Because the audience are directly involved with these issues, they are quite responsive to these discussions and have often provided unique solutions to common problems. Technical workshops are co-sponsored by local municipalities - these day-long workshops are hosted by a municipality and include managers from other municipalities, the local water authority, and local community leaders. Additional activities include: technical advice on water infrastructure projects is given; there are educational exchanges between local and international students, scientists, natural resource managers, and community leaders; and synthesis publications relevant to integrated water resource management are produced. Other activities have included compiling oral environmental histories and organising watershed restoration activities. This paper describes these activities and discusses the benefits and costs of each approach.
Geography and associated hydrological, hydroclimate and land-use
conditions and their changes determine the states and dynamics of wetlands
and their ecosystem services. The influences of these ...controls are not
limited to just the local scale of each individual wetland but extend over
larger landscape areas that integrate multiple wetlands and their total
hydrological catchment – the wetlandscape. However, the data and knowledge
of conditions and changes over entire wetlandscapes are still scarce,
limiting the capacity to accurately understand and manage critical wetland
ecosystems and their services under global change. We present a new
Wetlandscape Change Information Database (WetCID), consisting of geographic,
hydrological, hydroclimate and land-use information and data for 27
wetlandscapes around the world. This combines survey-based local information
with geographic shapefiles and gridded datasets of large-scale hydroclimate
and land-use conditions and their changes over whole wetlandscapes.
Temporally, WetCID contains 30-year time series of data for mean monthly
precipitation and temperature and annual land-use conditions. The
survey-based site information includes local knowledge on the wetlands,
hydrology, hydroclimate and land uses within each wetlandscape and on the
availability and accessibility of associated local data. This novel database
(available through PANGAEA https://doi.org/10.1594/PANGAEA.907398; Ghajarnia
et al., 2019) can support site assessments; cross-regional comparisons; and
scenario analyses of the roles and impacts of land use, hydroclimatic and
wetland conditions, and changes in whole-wetlandscape functions and ecosystem
services.
Climate change and human pressures are changing the global distribution and the extent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES ...are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico‐chemical changes (preconditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experimentally simulated, under standard laboratory conditions, rewetting of leaves, riverbed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative characteristics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dissolved substances during rewetting events (56%–98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contributed most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached OM. The opposite pattern was found in the arid zone. Environmental variables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached substances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying events.
In this study we experimentally simulated under laboratory conditions rewetting of leaves, riverbed sediments, and epilithic biofilms collected during the dry phase from intermittent rivers and ephemeral streams covering global spatial scale. We determined the amounts and quality of the leached nutrients and dissolved organic matter, assessed their inter‐substrate and cross‐climate differences, and estimated areal fluxes from 1 m2 of riverbeds. In addition, we evaluated the variance in leachate characteristics related to selected environmental variables and substrate characteristics.
El mapeo de manglares es la base para la zonificación con fines de manejo sostenible a escala sub-nacional. Sin embargo, muchas autoridades ambientales no cuentan con cartografía actualizada de ...manglares y usualmente el presupuesto disponible para la validación de campo es limitado. El objetivo de este artículo fue estimar el desempeño del Índice de Vegetación de Manglar (IVM) para la actualización de la extensión del manglar en un área semi-árida del Caribe Sur. Se empleó el departamento de Sucre (Colombia) como ejemplo para la reconstrucción multi-temporal (2017-2021) basada en el IVM, imágenes Sentinel 2 y cómputo en Google Earth Engine. La validación de campo fue asistida con sobrevuelos de un vehículo aéreo no tripulado de bajo costo (DJI Phantom 3 Advanced) para observar áreas de difícil acceso en el interior de parches grandes. La extensión del manglar varió significativamente entre temporadas de lluvia y sequía, producto del cambio de verdor. Mediante la construcción de un mosaico multi-temporal se estimaron 8924 ha (coeficiente Kappa: 0.78), cubriendo todas las categorías de manejo. Comparaciones con estimaciones previas realizadas por esfuerzos globales y nacionales mostraron un alto grado de consistencia. Se concluyó que el método, pese a su simplicidad, es una alternativa rápida para actualizar las zonificaciones de manglares en regiones semiáridas de Colombia. Se discuten las ventajas y desventajas del método.
Wetlands are often vital physical and social components of a country’s natural capital, as well as providers of ecosystem services to local and national communities. We performed a network analysis ...to prioritize Sustainable Development Goal (SDG) targets for sustainable development in iconic wetlands and wetlandscapes around the world. The analysis was based on the information and perceptions on 45 wetlandscapes worldwide by 49 wetland researchers of the Global Wetland Ecohydrological Network (GWEN). We identified three 2030 Agenda targets of high priority across the wetlandscapes needed to achieve sustainable development: Target 6.3—“Improve water quality”; 2.4—“Sustainable food production”; and 12.2—“Sustainable management of resources”. Moreover, we found specific feedback mechanisms and synergies between SDG targets in the context of wetlands. The most consistent reinforcing interactions were the influence of Target 12.2 on 8.4—“Efficient resource consumption”; and that of Target 6.3 on 12.2. The wetlandscapes could be differentiated in four bundles of distinctive priority SDG-targets: “Basic human needs”, “Sustainable tourism”, “Environmental impact in urban wetlands”, and “Improving and conserving environment”. In general, we find that the SDG groups, targets, and interactions stress that maintaining good water quality and a “wise use” of wetlandscapes are vital to attaining sustainable development within these sensitive ecosystems.
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