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Damming deltas: A practice of the past? Towards nature-based flood defense

Citation: van Wesenbeeck, B. K., Mulder, J. P. M., Marchand, M., Reed, D. J., de Vries, M. B., de Vriend, H. J., & Herman, P. M. J. (2014). Damming deltas: A practice of the past? Towards nature-based flood defenses. Estuarine, Coastal and Shelf Science, 140, 1–6. 
Estuarine, Coastal and Shelf Science - Vol. 140
There is extensive experience in adaptive management of exposed sandy coastlines through sand nourishment for coastal protection. However, in complex estuarine systems, coastlines are often shortened through damming estuaries to achieve desired safety levels. The Dutch Deltaworks illustrate that this approach disrupts natural sediment fluxes and harms ecosystem health, which negatively affects derived ecosystem services, such as freshwater availability and mussel and oyster farming. This heavily impacts local communities and thus requires additional maintenance and management efforts. Nevertheless, the discussion on coastline shortening keeps surfacing when dealing with complex coastal management issues throughout the world. Although adaptive delta management accompanied by innovative approaches that integrate coastal safety with ecosystem services is gaining popularity, it is not yet common practice to include adaptive pathways, a system-based view and ecosystem knowledge into coastal management projects. Here, we provide a first attempt to integrate ecosystem-based flood risk reduction measures in the standard suite of flood risk management solutions, ranging from structural to non-structural. Additionally, for dealing with the dynamic and more unpredictable nature of ecosystems, we suggest the adaptive delta management approach that consists of flexible measures, measurable targets, monitoring and intervention, as a framework for embedding ecosystem-based alternatives for flood risk mitigation in the daily practice of engineers and coastal planners.

Do green spaces affect the spatiotemporal changes of PM2.5 in Nanjing?

Citation: Chen, J., Zhu, L., Fan, P., Tian, L., Lafortezza, R., 2016. Do green spaces affect the spatiotemporal changes of PM2.5 in Nanjing? Ecol. Process. 5. doi:10.1186/s13717-016-0052-6
Chen J., Zhu L., Fan P., Tian L., Lafortezza R., Ecological Processes, 2016
Introduction: Among the most dangerous pollutants is PM2.5, which can directly pass through human lungs and move into the blood system. The use of nature-based solutions, such as increased vegetation cover in an urban landscape, is one of the possible solutions for reducing PM2.5 concentration. Our study objective was to understand the importance of green spaces in pollution reduction. Methods: Daily PM2.5 concentrations were manually collected at nine monitoring stations in Nanjing over a 534-day period from the air quality report of the China National Environmental Monitoring Center (CNEMC) to quantify the spatiotemporal change of PM2.5 concentration and its empirical relationship with vegetation and landscape structure in Nanjing. Results: The daily average, minimum, and maximum PM2.5 concentrations from the nine stations were 74.0, 14.2, and 332.0 μg m−3, respectively. Out of the 534 days, the days recorded as “excellent” and “good” conditions were found mostly in the spring (30.7 %), autumn (25.6 %), and summer (24.5 %), with only 19.2 % of the days in the winter. High PM2.5 concentrations exceeding the safe standards of the CNEMC were recorded predominately during the winter (39.3–100.0 %). Our hypothesis that green vegetation had the potential to reduce PM2.5 concentration was accepted at specific seasons and scales. The PM2.5 concentration appeared very highly correlated (R2 > 0.85) with green cover in spring at 1–2 km scales, highly correlated (R2 > 0.6) in autumn and winter at 4 km scale, and moderately correlated in summer (R2 > 0.4) at 2-, 5-, and 6-km scales. However, a non-significant correlation between green cover and PM2.5 concentration was found when its level was >75 μg m−3. Across the Nanjing urban landscape, the east and southwest parts had high pollution levels. Conclusions: Although the empirical models seemed significant for spring only, one should not devalue the importance of green vegetation in other seasons because the regulations are often complicated by vegetation, meteorological conditions, and human activities. © 2016, Chen et al.

Do small green roofs have the possibility to offer recreational and experiential benefits in a dense urban area? A case study in Helsinki, Finland.

Citation: Mesimäki M., Hauru K. & Lehvävirta S. (2018). Do small green roofs have the possibility to offer recreational and experiential benefits in a dense urban area? A case study in Helsinki, Finland. Urban Forestry & Urban Greening.
Growing and densifying cities set challenges for preserving and enhancing sufficient and good quality green urban environment. Rooftops offer vacant room for additional urban greening that may contribute to the well-being of people and the liveability of cities, but this potential lacks empirical support. In spite of the fact that even small green spaces produce, for example restorative experiences, the literature concerning the experiential and recreational benefits of green roofs is still scarce. To identify the experiential potential of a small urban green roof we explored restorative and other experiences of 178 people visiting a sparsely vegetated green roof in the centre of Helsinki, Finland, using a questionnaire. We showed that the studied green roof provided restorative and other positive experiences to the visitors. The level of perceived restorativeness was relatively high. In addition, the results revealed multiple perceived qualities that reflected visual as well as other sensory experiences, beauty, suitability of the place for oneself and the urban context, nature, desire to explore the place and interestedness, positive excitement, and safety. Furthermore, answers to the open questions revealed a wide range of other observations and feelings, such as peace, joy, excitement and hope. Our study indicates that even a small and rather ascetic accessible green roof has potential to offer a moment of respite in the middle of urban everyday hassle, thus implying that these kinds of solutions may allow for a pinch of beneficial green in places where more diverse and lusher solutions are not possible due to, e.g. the load capacity of a roof.

Does "greening" of neotropical cities considerably mitigate carbon dioxide emissions? The case of Medellin, Colombia

Citation: Reynolds, C.C., Escobedo, F.J., Clerici, N., Zea-Camaño, J., 2017. Does “greening” of neotropical cities considerably mitigate carbon dioxide emissions? The case of Medellin, Colombia. Sustain. 9. doi:10.3390/su9050785
Reynolds C.C., Escobedo F.J., Clerici N., Zea-Camaño J., Sustainability (Switzerland), 2017
Cities throughout the world are advocating highly promoted tree plantings as a climate change mitigation measure. Assessing the carbon offsets associated with urban trees relative to other climate change policies is vital for sustainable development, planning, and solving environmental and socio-economic problems, but is difficult in developing countries. We estimated and assessed carbon dioxide (CO2) storage, sequestration, and emission offsets by public trees in the Medellin Metropolitan Area, Colombia, as a viable Nature-Based Solution for the Neotropics. While previous studies have discussed nature-based solutions and explored urban tree carbon dynamics in high income countries, few have been conducted in tropical cities in low-middle income countries, particularly within South America. We used a public tree inventory for the Metropolitan Area of the Aburrá Valley and an available urban forest functional model, i-Tree Streets, calibrated for Colombia's context. We found that CO2 offsets from public trees were not as effective as cable cars or landfills. However, if available planting spaces are considered, carbon offsets become more competitive with cable cars and other air quality and socio-economic co-benefits are also provided. The use of carbon estimation models and the development of relevant carbon accounting protocols in Neotropical cities are also discussed. Our nature-based solution approach can be used to better guide management of urban forests to mitigate climate change and carbon offset accounting in tropical cities lacking available information. © 2017 by the authors.

Drivers and trajectories of land cover change in East Africa: Human and environmental interactions from 6000 years ago to present

Citation: Marchant, R., Richer, S., Boles, O., Capitani, C., Courtney-Mustaphi, C.J., Lane, P., Prendergast, M.E., Stump, D., De Cort, G., Kaplan, J.O., Phelps, L., Kay, A., Olago, D., Petek, N., Platts, P.J., Punwong, P., Widgren, M., Wynne-Jones, S., Ferro-Vázquez, C., Benard, J., Boivin, N., Crowther, A., Cuní-Sanchez, A., Deere, N.J., Ekblom, A., Farmer, J., Finch, J., Fuller, D., Gaillard-Lemdahl, M.-J., Gillson, L., Githumbi, E., Kabora, T., Kariuki, R., Kinyanjui, R., Kyazike, E., Lang, C., Lejju, J., Morrison, K.D., Muiruri, V., Mumbi, C., Muthoni, R., Muzuka, A., Ndiema, E., Kabonyi Nzabandora, C., Onjala, I., Schrijver, A.P., Rucina, S., Shoemaker, A., Thornton-Barnett, S., van der Plas, G., Watson, E.E., Williamson, D., Wright, D., 2018. Drivers and trajectories of land cover change in East Africa: Human and environmental interactions from 6000 years ago to present. Earth-Science Rev. 178, 322–378. doi:10.1016/j.earscirev.2017.12.010
Marchant R., Richer S., Boles O., Capitani C., Courtney-Mustaphi C.J., Lane P., Prendergast M.E., Stump D., De Cort G., Kaplan J.O., Phelps L., Kay A., Olago D., Petek N., Platts P.J., Punwong P., Widgren M., Wynne-Jones S., Ferro-Vázquez C., Benard J., B
East African landscapes today are the result of the cumulative effects of climate and land-use change over millennial timescales. In this review, we compile archaeological and palaeoenvironmental data from East Africa to document land-cover change, and environmental, subsistence and land-use transitions, over the past 6000 years. Throughout East Africa there have been a series of relatively rapid and high-magnitude environmental shifts characterised by changing hydrological budgets during the mid- to late Holocene. For example, pronounced environmental shifts that manifested as a marked change in the rainfall amount or seasonality and subsequent hydrological budget throughout East Africa occurred around 4000, 800 and 300 radiocarbon years before present (yr BP). The past 6000 years have also seen numerous shifts in human interactions with East African ecologies. From the mid-Holocene, land use has both diversified and increased exponentially, this has been associated with the arrival of new subsistence systems, crops, migrants and technologies, all giving rise to a sequence of significant phases of land-cover change. The first large-scale human influences began to occur around 4000 yr BP, associated with the introduction of domesticated livestock and the expansion of pastoral communities. The first widespread and intensive forest clearances were associated with the arrival of iron-using early farming communities around 2500 yr BP, particularly in productive and easily-cleared mid-altitudinal areas. Extensive and pervasive land-cover change has been associated with population growth, immigration and movement of people. The expansion of trading routes between the interior and the coast, starting around 1300 years ago and intensifying in the eighteenth and nineteenth centuries CE, was one such process. These caravan routes possibly acted as conduits for spreading New World crops such as maize (Zea mays), tobacco (Nicotiana spp.) and tomatoes (Solanum lycopersicum), although the processes and timings of their introductions remains poorly documented. The introduction of southeast Asian domesticates, especially banana (Musa spp.), rice (Oryza spp.), taro (Colocasia esculenta), and chicken (Gallus gallus), via transoceanic biological transfers around and across the Indian Ocean, from at least around 1300 yr BP, and potentially significantly earlier, also had profound social and ecological consequences across parts of the region. Through an interdisciplinary synthesis of information and metadatasets, we explore the different drivers and directions of changes in land-cover, and the associated environmental histories and interactions with various cultures, technologies, and subsistence strategies through time and across space in East Africa. This review suggests topics for targeted future research that focus on areas and/or time periods where our understanding of the interactions between people, the environment and land-cover change are most contentious and/or poorly resolved. The review also offers a perspective on how knowledge of regional land-use change can be used to inform and provide perspectives on contemporary issues such as climate and ecosystem change models, conservation strategies, and the achievement of nature-based solutions for development purposes. © 2018 Elsevier B.V.

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