National University of San Antonio Abad

Tropical ecosystems are major sources of the greenhouse gases (GHGs) methane (CH4) and nitrous oxide (N2O), which are 25 and 298 times more effective than carbon dioxide (CO2), respectively, in trapping long-wave radiation in the atmosphere. Increases in CH4 and N2O concentrations since the start of the Industrial Revolution are responsible for over one-third of global warming, and future changes in the atmospheric budgets of these GHGs have implications for the Earth's climate and environmental conditions. N2O emissions, in particular, are projected to rise in the future due to agricultural expansion and enhanced atmospheric nitrogen deposition. Recent studies of the global budgets of CH4 and N2O using satellite imagery, atmospheric measurements, and modelling suggest that significantly more CH4 and N2O are released from the tropics than previously thought due to unaccounted sources of CH4 and N2O. It is critical for us to identify and characterise these 'missing' sources if we wish to understand the current contribution of the tropics to GHG budgets. Knowledge of these 'missing' sources is also necessary for predicting how tropical GHG emissions are likely to respond to future environmental or climatic change. One strong potential candidate for these 'missing' sources of CH4 and N2O are tropical uplands. Tropical uplands have been conspicuously absent from existing atmospheric budgets, because scientific attention has largely focused on CH4 and N2O emissions from lowland forests, savannas, or wetlands. Studies from tropical uplands suggest that they are potentially large sources of CH4 and N2O, with emissions that are equal to or greater than those from lowland environments. Upland rainforests in Puerto Rico, for example, emit more CH4 than lowland forests, with emission rates that are on par with northern wetlands, the largest natural sources of CH4 worldwide. To address these gaps in knowledge, we will conduct a comprehensive study of CH4 and N2O cycling in the Peruvian Andes, using a mixture of field measurements, controlled environment studies, and mathematical modelling. Specifically, we will: 1. Investigate how CH4 and N2O fluxes vary in space and time along an environmental gradient that spans 3000 m of altitude, from lowland rainforest to upper montane rainforest. 2. Explore how key environmental variables (e.g., plant productivity, climate, soil moisture, carbon and nitrogen availability, oxygen) influence CH4 and N2O emissions. 3. Determine if existing mathematical models are able to simulate CH4 and N2O emissions from tropical ecosystems, adapting these models as necessary to better simulate field observations. 4. Determine if GHG emissions from the Andes are able to account for some of the 'missing' tropical sources of CH4 and N2O by extrapolating our field observations to the regional scale using a combination of mathematical modelling, satellite imagery, and land cover databases (i.e., GIS). The proposed research will greatly advance our understanding of CH4 and N2O emissions for an important but understudied region, and will help us determine the relative contribution of Andean ecosystems to the CH4 and N2O budgets for South America. Knowledge of the emission rates and environmental controls on CH4 and N2O fluxes from upland Andean ecosystems will also help us evaluate whether other tropical uplands are likely to be sources of CH4 and N2O, and assess their potential contributions to the global atmospheric budgets of CH4 and N2O. Lastly, the development and adaptation of mathematical models that accurately simulate tropical CH4 and N2O fluxes will allow us to predict the likely response of tropical uplands to future environmental or climatic change.

This project will advance our ability to quantify the influence of phosphorus limitation and temperature on plant tissue respiration. The carbon balance of an organism and of an ecosystem is strongly dependent on the balance between photosynthesis and respiration. Globally, respiration on land is at present very slightly smaller than photosynthesis, meaning that terrestrial ecosystems are thought to be a 'sink' for atmospheric carbon dioxide, slowing the continual rise in carbon dioxide concentration in the atmosphere. A large fraction of the total respiration from land is thought to come from trees, so understanding what determines plant respiration is central to understanding how the terrestrial component of the Earth system works. However, despite its importance, only a limited amount of data are available to help us quantify plant respiration over large regions of the world. For example, although we know that the most important nutrients for plant growth (nitrogen and phosphorus) limit plant metabolism, we have almost no information on how phosphorus deficiency limits plant respiration, and hence the carbon balance. We also know only a little about how plant respiration responds to temperature: currently our global models of terrestrial ecosystems make large assumptions about this that may be wrong. When we consider that: (i) 30% of the global land surface may be phosphorus-deficient; (ii) the global phosphorus supply may seriously decline in under 100 years; and (iii) global climatic warming is likely to increase plant respiration this century (but by how much we don't know), there is clearly a strong and urgent need to address this issue. We will make measurements of respiration on a wide range of plant species. We will first use controlled-environment chambers to control the supply of nutrients to plants. We will then couple this with field measurements made in selected forested regions where phosphorus and nitrogen are differentially limiting, in order to compare the data from our experimental work to real ecosystems. The choice of our fieldsites in tropical South America and New Zealand makes use of existing knowledge about likely phosphorus limitations and will allow us to also address the issue of how biodiversity affects the phosphorus-respiration relationship. Finally we will analyse our data to enable us to incorporate our findings into mathematical models used to calculate how the land surface and our climate interact. Our project will enable us: (i) to quantify how phosphorus deficiency affects respiration; (ii) to quantify the influence of phosphorus deficiency on the temperature dependence of plant respiration. We will be able to link our results to existing work on the relationship between plant tissue metabolism and nitrogen concentration, and to incorporate the results into site-specific and global modelling frameworks. The project is highly cost efficient to NERC, making use of international facilities and project partner time supplied at zero cost to this project. This work will also link directly into existing research programmes funded by NERC of which the project investigators are already a part. The project will fill a signficant gap in our understanding of global ecology and the functioning of the Earth system.

Tropical ecosystems are major sources of the greenhouse gases (GHGs) methane (CH4) and nitrous oxide (N2O), which are 25 and 298 times more effective than carbon dioxide (CO2), respectively, in trapping long-wave radiation in the atmosphere. Increases in CH4 and N2O concentrations since the start of the Industrial Revolution are responsible for over one-third of global warming, and future changes in the atmospheric budgets of these GHGs have implications for the Earth's climate and environmental conditions. N2O emissions, in particular, are projected to rise in the future due to agricultural expansion and enhanced atmospheric nitrogen deposition. Recent studies of the global budgets of CH4 and N2O using satellite imagery, atmospheric measurements, and modelling suggest that significantly more CH4 and N2O are released from the tropics than previously thought due to unaccounted sources of CH4 and N2O. It is critical for us to identify and characterise these 'missing' sources if we wish to understand the current contribution of the tropics to GHG budgets. Knowledge of these 'missing' sources is also necessary for predicting how tropical GHG emissions are likely to respond to future environmental or climatic change. One strong potential candidate for these 'missing' sources of CH4 and N2O are tropical uplands. Tropical uplands have been conspicuously absent from existing atmospheric budgets, because scientific attention has largely focused on CH4 and N2O emissions from lowland forests, savannas, or wetlands. Studies from tropical uplands suggest that they are potentially large sources of CH4 and N2O, with emissions that are equal to or greater than those from lowland environments. Upland rainforests in Puerto Rico, for example, emit more CH4 than lowland forests, with emission rates that are on par with northern wetlands, the largest natural sources of CH4 worldwide. To address these gaps in knowledge, we will conduct a comprehensive study of CH4 and N2O cycling in the Peruvian Andes, using a mixture of field measurements, controlled environment studies, and mathematical modelling. Specifically, we will: 1. Investigate how CH4 and N2O fluxes vary in space and time along an environmental gradient that spans 3000 m of altitude, from lowland rainforest to upper montane rainforest. 2. Explore how key environmental variables (e.g., plant productivity, climate, soil moisture, carbon and nitrogen availability, oxygen) influence CH4 and N2O emissions. 3. Determine if existing mathematical models are able to simulate CH4 and N2O emissions from tropical ecosystems, adapting these models as necessary to better simulate field observations. 4. Determine if GHG emissions from the Andes are able to account for some of the 'missing' tropical sources of CH4 and N2O by extrapolating our field observations to the regional scale using a combination of mathematical modelling, satellite imagery, and land cover databases (i.e., GIS). The proposed research will greatly advance our understanding of CH4 and N2O emissions for an important but understudied region, and will help us determine the relative contribution of Andean ecosystems to the CH4 and N2O budgets for South America. Knowledge of the emission rates and environmental controls on CH4 and N2O fluxes from upland Andean ecosystems will also help us evaluate whether other tropical uplands are likely to be sources of CH4 and N2O, and assess their potential contributions to the global atmospheric budgets of CH4 and N2O. Lastly, the development and adaptation of mathematical models that accurately simulate tropical CH4 and N2O fluxes will allow us to predict the likely response of tropical uplands to future environmental or climatic change.

The Peruvian Andes is home to 71% of the world's tropical glaciers, and the meltwater they supply is an essential resource for people downstream who depend on it for irrigation and sanitation. Further, hydropower plants driven by glacial meltwater provide more than 40% of Peru's electricity. However, Peru's glaciers are receding rapidly, threatening this supply, as well as releasing sediment to valley areas and revealing topographic depressions that may become natural reservoirs for glacier runoff. These thawing landscapes are also very active and can pose risks to downstream people and infrastructure. PEGASUS will assess the opportunities and threats that rapidly evolving landscapes, and natural resources, will bring to the people and businesses of three glacierised Cordilleras of the Peruvian Andes - Urubamba, Vilcabamba and Vilcanota - and make recommendations that will maximise the potential prosperity that can be gained in the face of continued environmental change. Modelling the climate of mountain catchments such as those in Peru is complex because of the interaction of large-scale weather systems with local-scale winds and extreme relief. Uncertainties in modelling the climate feed into projections of glacier change, which themselves are limited by a lack of data on previous glacier behaviour for calibration, and downstream river flows for validation. Robust climate modelling is also required for predictions of permafrost (freezing) heights, which are a key control on ice and bedrock stability, and thus avalanche risk. PEGASUS will produce new and refined projections of climate that will drive cutting edge glacier and permafrost models, to yield firm predictions of how the glaciers and freezing levels will change on a 5-yearly interval from now until the end of the century. As the glaciers recede and hillslopes become more active, sediment will be released into the valleys, and lakes will develop where ice existed. Some of the sediment will be trapped within these glacial lakes, and some will be transferred downstream by river flows. The rate of sediment release by glaciers in advanced states of recession is poorly known, and the role of lakes in capturing the sediment is also poorly quantified. PEGASUS will perform field measurements and modelling to improve understanding of the role of glacial lakes in removing, conveying and storing sediment being released from the glaciers, and characterise the impact this will have on downstream water quality and critical hydropower infrastructure. The locations of future glacial lakes can be predicted by modelling the thickness of the current glaciers and identifying subglacial depressions that will be revealed as the ice recedes. Using a Digital Elevation Model (DEM) of this ice-free terrain, it is possible to make a quantitative assessment of the hazard that these new lakes, as well as existing glacial lakes, pose to downstream areas if they were to burst catastrophically. PEGASUS will carry out this assessment for the largest lakes in the Urubamba-Vicabamba-Vilcanota study area and then undertake additional fine-resolution and physically-based numerical modelling to robustly quantify the effects of flooding and debris flows on people, land, the downstream river dynamics, and hydropower infrastructure. PEGASUS will then identify the barriers and opportunities that exist to the use of these lakes for water storage and hydropower development. This assessment will integrate consultations with government (CORECC), a large hydropower company (EGEMSA) and, crucially, communities living in the catchments of the lakes we have analysed. The recommendations that follow will provide information on the sustainability of existing and future hydropower schemes, how to manage water use in future decades and formulate policies that reflect the needs of all stakeholders, and the potential hazards that unstable mountain environments may pose to lives and livelihoods in future years.

The anticipated impacts of climate-change induced glacier shrinkage on the water security of mountains and downstream lowlands is a major global concern. However, the connections between climate change, glacier shrinkage, water security and local adaptive capacity are multi-dimensional and non-linear. In many regions of the world including Peru, the physical and human processes that govern them are poorly understood. Therefore, understanding these process, their impacts and implementing adequate science-based adaptation strategies requires an interdisciplinary approach. This approach should combine advancing the state-of-the-art of glaciological and hydrological process understanding, with new insights in current and future levels of water security, human vulnerability, and adaptive capacity. We propose to address this challenge by developing an integrated glacier - water security assessment model to transform our understanding of the impact of glacier shrinkage on water security and to inform policy practices in Peru. We identify the lack of glaciological, hydro-climatological, and water resources data as a major bottleneck to achieve this. Therefore, we propose participatory water resources monitoring as a radically new approach to transform our knowledge of physical processes, constraining water resources models, and supporting evidence-based policy-making. We have assembled a world-leading consortium that combines high-level expertise in field monitoring and computer simulation of glaciers and water resources in Peru, with pioneers of participatory data collection for sustainable development and policy-support. This consortium is ideally placed to generate a breakthrough in data availability on the link between glacier reduction and current and future water security. This is needed to build the next generation of glaciological and hydrological models that can support the design and implementation of adequate climate adaptation strategies. We will use the Vilcanota-Urubamba Basin in southern Peru as our case study. This basin hosts the largest tropical ice cap (Quelccaya) and it is characterised by a very complex water management context and high data scarcity. Our project will follow a "source to tap" paradigm, in which we will deliver the first fully integrated water resources vulnerability assessment framework for glacier-fed basins, comprising state-of-the-art glaciology, hydrology, water demand characterisation, and water security assessment. We will design targeted glacio-hydrological and water resources monitoring campaigns, to complemented existing monitoring efforts of our project partners and collaborators, and new remotely sensed data sets. This campaign will be implemented using the principles and tools of participatory monitoring and knowledge co-creation that our team has pioneered in the tropical Andes. The datasets produced by this approach, combined with existing monitoring implemented by our team and collaborators, will allow us to build an integrated water supply-demand-vulnerability assessment model for glacierized basins, and to use this to evaluate adaptation strategies at the local scale. For the latter, we have engaged with a set of policy stakeholders in Peru that play a key role in the implementation of recent transformative legislation on Peruvian water resources management, and in particular in the new law on the implementation of water funds to invest in catchment interventions (Law 30215). Working directly with these stakeholders will ensure that our approach focuses on locally relevant adaptation strategies, including novel approaches such as the use of nature-based solutions and the restoration of ancestral water "seeding and harvesting practices", thus providing both the scientific basis and the operational tools that support the implementation of this legal framework.