Urban Encroachment Research Articles

Urban sprawl and agricultural livelihood response in peri-urban Ghana

ABSTRACT The paper examines agricultural livelihood effects of urban sprawl and farmers' response in peri-urban Kumasi, Ghana, involving in-depth interviews with sixty farmers (n = 60) and four key informants (n = 4). Greater Kumasi has expanded spatially over time resulting in arable land reduction in the peri-urban interface and affecting households in varying ways. This has evoked different responses from affected farmers including agricultural intensification, extensification, diversification and adoption of off-farm livelihood strategies. While some households made livelihood gains in their response, and some livelihood losses, others neither gained nor lost. A mix of livelihood assets, but more importantly human and social capital, were identified as key determinants of the outcomes of households’ livelihood strategies employed. To protect arable land from urban encroachment and reduce peri-urban households’ vulnerabilities the following policy interventions are noteworthy: effective spatial planning through institutional strengthening, legislative enforcement and widening market for agricultural goods and expanding non-farm jobs.

THE URBAN SPRAWL ON AGRICULTURAL LANDS IN GHARBIA GOVORNORATE

This study focuses on the evolution of urban encroachment on arable land in Egypt. There are three forms of encroachment on arable land. The first type is the removal of the fertile topsoil of agricultural land for the main purpose of bricks manufacturing. The second type is the setting aside of arable land and letting the land go unproductive for long time periods. The third type is the permanent conversion of arable land to buildings. The total acreage lost to encroachment from January 25, 2011 revolution till November 18, 2018 is about 85 thousands feddans of fertile land. The first type of topsoil removal constitutes 7.7 percent of the total lost acreage .While setting aside of arable land constitutes 35.5 percent and the conversion of arable land to buildings constitutes 57.8 percent of total land lost to encroachment . Rapid population growth is the main driver for accelerating encroachment on arable land in Egypt. This is especially evident in the governorates that are not endowed with desert backyard. Gharbeya governorate is a good example of densely populated regions with no desert backyard that could be used for urban expansion. The study reveals that population in Gharbeya grew during the period 2006-2017 with an annually rate of 2.1 percent. While cultivated area and cropped area declined with an annual rate of 1006 feddans and 2992 feddans respectively during the same time period. The continued encroachment on agricultural land is a major threat to Egypt’s food security due to the limited base of arable land in Egypt. In fact per capita share of arable land is declining very rapidly over the years. For example, the ratio of population to arable land increased from 10.4 in 2006 to 15.4 in 2017. The country is attempting to make up for the lost land through reclamation of desert land. Unfortunately, reclamation of desert land is very expensive endeavor and requires major investment in basic infrastructure such as roads, irrigation networks, power grids, and social infrastructure. Therefore it is of utmost importance for the government to pay due attention to the problem of urban encroachment on old arable land and devise policies and legislations that would put a brake on this phenomena .

The historical use of fire as a land management tool in New Zealand and the challenges for its continued use

New Zealand’s use of fire as a land management tool has had an extensive and lasting impact on New Zealand’s rural landscapes. We reviewed the historical rural use of fire by Māori and Europeans in NZ, discuss the challenges facing its future use as a land management tool and briefly compare with the international situation. We conducted a search using keywords and databases to review research articles on the historical use of fire in NZ. NZ experienced an historical two-phase anthropogenic use of fire as a land management tool since human arrival (c. 1280–1350 AD). In a forested non-fire adaptive environment, the widespread and intensive use of fire reduced natural forest cover from 85 to 90% prior to human arrival to 25% by the mid-twentieth century. Māori primarily used fire to clear travel routes, hunt for game, maintain bracken beds and clear land for crops. Europeans introduced a renewed era of burning, primarily for land conversion to agriculture, pasture regeneration, fuel load reduction, pest control and removing vegetation residues. Concerns regarding fire escapes, risks to infrastructure, environmental impacts, urban encroachment into rural environments and climate change may influence future use. NZ differs from other countries where fire is a natural component of the landscape, limiting its application as a tool for landscape restoration and its use on conservation land remains contentious. A third-phase use of fire is emerging in the rural sector, targeting niche burning for a range of specific purposes under the challenge of increasing environmental, social and regulatory constraints.

A proposal for the use of Core and Buffer Zones to protect the heritage of the Cyrenean landscapes

AbstractThe ancient landscapes surrounding Cyrene, which have been incredibly well preserved for centuries, have suffered more destructions in the past 7 or 8 years than in the whole of the last millennium. Urban encroachment, strong demographic pressure, unsustainable exploitation of resources and unplanned growth of infrastructures and services are threatening the archaeological heritage of this splendid site. The Department of Antiquities (DoA) has always struggled against these phenomena, but today the destructions are so great that the DoA is often powerless to act. This paper continues previous works on the damage to the Cyrenean necropoleis after 2011(Abdulkariem and Bennett, 2014; Al Raeid et al. 2016; Menozzi, Di Valerio et al. 2017; Menozzi, Tamburrino et al. 2017) and proposes strategies to help, on the basis of a preliminary report organised by the Mission of the University of Chieti in collaboration with the Departments of Antiquities of Cyrene and Tripoli, as requested by UNESCO. This preliminary step towards further improvements and needs to be discussed with other institutions and missions. The first part presents a proposal for controlling the core and buffer zones around Cyrene; the second part is an update on the recent damages to the necropoleis.

Analysis of Chandigarh Periphery for the Urban Containment

The vision of great architect Le Corbusier for an agricultural greenbelt surrounding Chandigarh was to provide an outer beauty by linking rural India to the city. The goal of the greenbelt was to create distinction between rural and urban practices, although it has suffered to restrict expansion and protect functional rural landscape. Today, the symmetry of Chandigarh periphery is destroyed due to rapid urban encroachment and unregulated construction. The present conditions were surveyed, analyzed and solutions were prepared from the assessments of contemporary urban containment practices in the developed countries. All the solution was examined on the basis of their effectiveness. In this case if the assessed solutions are successfully implemented, the desired measures will provide agricultural protection, urban development and rural aspect.

PROPOSING DIGITAL MODELS FOR THE DISCUSSION OF CONTESTED CONSERVATION PRACTICE: CASE STUDIES FROM TAMIL NADU, INDIA

Abstract. This paper explores the potential for digital surveys to mediate as tools in a complex arena. As increased wealth and continuous religious practice have supported the energetic maintenance and renovation of temple buildings in Tamil Nadu justified by reference to ancient texts, UNESCO commissioned a fact-finding mission regarding conservation practice there in 2016. As part of wider project to investigate the strands of inherited textual guidance in this sensitive area, digital documentation methods are being tested in terms of their capacity to provide a locus for discourse between divergent views at a time of rapid formulation of policy documents that seek to offer guidelines for the conservation of an estimated 38000 temple buildings in the state. This paper outlines some challenges and ambitions of creating digital platforms to serve such an endeavour through potential scenarios offered by two case studies. Specifically, it considers the merits of tools to read urban encroachment, to identify change over time and to explore a means to provide a hypothetical platform for discussion of potentially sensitive adjustments.

Urban land use dynamics and change implication by using low-resolution LISS III imagery

Extension of urban areas is augmented reality. Identification of urban areas and mapping urban sprawl is directly related to population growth. Very frequent identification and monitoring of urban change are needed for urban governance and planners. The objective of the proposed paper was to extract the urban land cover by locating the human settlement areas and to develop a model to map potential spatio-temporal urban expansion. Multi-temporal imagery of Kalaburgai, state of Karnataka, India has been used for the work. The imagery was subjected for supervised fuzzy classification to extract spatial information of the urban area, Principal Component Analysis to transform the correlated components and lastly, unsupervised post classification on composite PCA images to separate uncorrelated pixels. Uncorrelated pixels depict the temporal change data. Results were satisfying, with 5.53 percentage area of urban change implications. Finally, the accuracy assessment of the proposed method shows promising results with an overall accuracy to be 80% and 0.78 for the kappa coefficient. Quantification of urban areas and probabilities of villages changing into cities can be done accurately by the proposed method. Significant urban expansion was observed by the results in Kalaburagi city from 2010 to 2013 with mostly vegetation changing into urban encroachment.

Monitoring Agricultural Expansion in a Newly Reclaimed Area in the Western Nile Delta of Egypt Using Landsat Imageries

Detection and monitoring land use/land cover (LULC) changes using historical multi-temporal remote sensing data is greatly important for providing an effective and robust assessment of the human-induced impacts on the environmental conditions. It is extremely recommended for LULC studies related to evaluating the sustainability of changing areas over time. The agricultural sector in Egypt is one of the crucial pillars of the national economy. The amount of traditional agricultural land (Old Lands) in the Nile Delta had a significant decline over the past few decades due to urban encroachment. Consequently, several land reclamation initiatives and policies have been adopted by the Egyptian government to expand agricultural land in desert areas (New Lands) adjacent to both fringes of the Nile delta. Tiba district is one of those newly reclaimed areas located in the western Nile Delta of Egypt with a total area of 125 km2. The primary objective of this article was to identify, monitor and quantify historical LULC changes in Tiba district using historical multi-temporal Landsat imageries for six different dates acquired from 1988 to 2018. The temporal and historical changes that occurred were identified using supervised maximum likelihood classification (MLC) approach. Three major LULC classes were distinguished and mapped: (1) Agricultural land; (2) barren land; and (3) urban land. In 1988, Tiba district was 100% barren land; however, during the 1990s, the governmental reclamation projects have led to significant changes in LULC. The produced LULC maps from performing the MLC demonstrated that Tiba district had experienced significant agricultural land expansion from 0% in 1988 to occupy 84% in 2018, whilst, barren land area has decreased from 100% in 1988 to occupy only 7% in 2018. This reflects the successful governmental initiatives for agricultural expansion in desert areas located in the western Nile Delta of Egypt.

Soil Security for Australia

Soil Security is an emerging sustainability science concept with global application for guiding integrated approaches to land management, while balancing ecosystem services, environmental, social, cultural, and economic imperatives. This discussion paper sets the scene for an Australian Soil Security framework as an example of how it might be developed for any country, defining the key issues and justification for Soil Security, as well as detailing implementation requirements and benefits; two examples of beneficial outcomes are provided in terms of facilitating decommoditization of agricultural products and the impact of urban encroachment on productive land. We highlight research gaps, where new knowledge will contribute to well-rounded approaches that reflect differing stakeholder perspectives. We also provide key nomenclature associated with a potential Soil Security framework so that future discussions may use a common language. Through this work we invite scientific and policy discourse with the aim of developing more informed responses to the myriad of competing demands placed on our soil systems.

Evaluation of urban encroachment on farmland: a threat to urban agriculture in Peshawar City District, Pakistan

Evaluation of urban encroachment on farmland: a threat to urban agriculture in Peshawar City District, Pakistan

Mosquito Control and Coastal Development: How they Have Coexisted and Matured in Florida and Australia.

The aims of this review were to compare planning for both mosquito control and land use in east-central Florida, USA, and in New South Wales, Queensland, and the Northern Territory, Australia. Saltwater mosquito production in mangroves and salt marsh is the predominant mosquito control concern in all the areas. Urban encroachment towards saltwater mosquito habitats is a problem in both Florida and Australia. In east-central Florida and the Northern Territory, mosquito control is supported by comprehensive source reduction programs, whereas in Queensland and New South Wales, larviciding is the main method of control. The long-term control by source reduction programs reduces vulnerability to mosquito issues as population encroaches towards wetlands, whereas larviciding programs have to respond repeatedly as problems arise. Problems from urban encroachment are exacerbated if mosquito control and land-use planning are not integrated. Further, urban planning that is not informed by mosquito management can lead to increased mosquito problems by inadvertent design or allowing residential development close to mosquito habitats. This increases the need for mosquito control and related resourcing. At the regional level of governance, Florida and the Northern Territory generally have greater integration between planning for development and mosquito control than at the local government level in New South Wales and Queensland, where there is a lack of integration between mosquito agencies and planners. It is concluded that coordination of planning and mosquito control is more effective at higher government levels than at local levels, which have less connectivity between management areas and/or insufficient resources. The lesson is that collaboration can assist in avoiding or resolving conflicts.

Impacts of Small-Scale Urban Encroachment on Air Temperature Observations

AbstractA field experiment was performed in Oak Ridge, Tennessee, with four instrumented towers placed over grass at increasing distances (4, 30, 50, 124, and 300 m) from a built-up area. Stations were aligned in such a way to simulate the impact of small-scale encroachment on temperature observations. As expected, temperature observations were warmest for the site closest to the built environment with an average temperature difference of 0.31° and 0.24°C for aspirated and unaspirated sensors, respectively. Mean aspirated temperature differences were greater during the evening (0.47°C) than during the day (0.16°C). This was particularly true for evenings following greater daytime solar insolation (20+ MJ day−1) with surface winds from the direction of the built environment where mean differences exceeded 0.80°C. The impact of the built environment on air temperature diminished with distance with a warm bias only detectable out to tower B′ located 50 m away. The experimental findings were comparable to a known case of urban encroachment at a U.S. Climate Reference Network station in Kingston, Rhode Island. The experimental and operational results both lead to reductions in the diurnal temperature range of ~0.39°C for fan-aspirated sensors. Interestingly, the unaspirated sensor had a larger reduction in diurnal temperature range (DTR) of 0.48°C. These results suggest that small-scale urban encroachment within 50 m of a station can have important impacts on daily temperature extrema (maximum and minimum) with the magnitude of these differences dependent upon prevailing environmental conditions and sensing technology.

Conservation and enhancement of the green infrastructure as a nature-based solution for Rome’s sustainable development

Three quarters of the European population live in urban areas, which is expected to increase to over 80% by 2050. The well-being of urban citizens appears to be closely linked to the correlation between the growth of urban areas and to the availability of green spaces. The conservation and the enhancement of the Green Infrastructure (GI) can be considered a Nature-Based Solution (NBS) to improve the sustainability of urban development. From this perspective, it is important to identify priority areas close to existing GIs suitable to be preserved from further urban encroachment. Our study aims to draw up a methodology to identify priority areas and, accordingly, to expand the GIs. The main objectives are: (i) to identify the most sensitive areas of the GI to be preserved from urban encroachment; (ii) to locate arable lands in the vacant border territories between GIs and built-up areas, that, if converted into connected elements, would enhance the connectivity of the existing GIs whilst limiting land take; (iii) to define an index of priorities for increasing the GI territory by means of NBSs, taking into account the variability of GI coverage and level of legal protection for nature conservation across different neighborhoods in the city. This approach is applied to the GIs of the 15 administrative units of the municipality of Rome (Italy) as a case study. First, we focus on Urban Atlas classes to map the GIs in the municipality. We then use Morphological Spatial Pattern Analysis, implemented by a free software toolbox GUIDOS, to identify the key components of the GIs, such as hubs (core areas) and links (bridges). Then, a simulated new scenario is provided by including within the current GIs the agricultural lands outside protected areas, but within a buffer zone of 300 m from the land take. If the aforementioned agricultural lands, amounting to about 8000 ha, were converted into GI elements, they could lead to the improvement of connectivity and limit land take. Finally, in order to expand the area of the GIs, priority areas are selected within each administrative unit using an index based on the budget allocation process. The proposed methodology could be used: (i) by decision makers, looking for NBS in the design and planning of sustainable development of the city; and (ii) to enhance GI connectivity.

Temporal detection and prediction of agricultural land consumption by urbanization using remote sensing

The most fertile land in Egypt is under continuous loss by urbanization. In some countries, this could be considered normal, but in Egypt, it is a severe violation of the country’s limited agricultural land. The main objectives of this research are to quantify the agricultural land consumption by urbanization and predict the future pattern of this process in some parts of Alexandria and El-Behiera governorates using the Landsat satellite images of 1987, 2001, 2015, and 2019. Image classification was performed using the Maximum likelihood supervised classification technique. Five land use/cover (LULC) types have been identified, which are agriculture, urban, gardens, the international road, and water. Classification results were further enhanced by employing post-classification and filtering processes which increased classification accuracy and minimized urban land use overestimation. Four LULC maps have been developed for 1987, 2001, 2015 and 2019. A post-classification comparison method was applied to detect the LULC changes among the independently classified images and quantify the loss of agricultural land by urbanization. Prediction of urban encroachment to agricultural land was performed by Land Change Modeler basing on both the past change trend of urbanization and the influencing distance-to-urban factor. The future LULC prediction maps for 2019, 2050, and 2100 have been generated. Prediction validity was applied using actual vs predicted LULC 2019 maps. The results indicated that the agricultural and urban categories are the prevailing LULC types in the investigated area. Over the last three decades significant loss in the agricultural land was observed together with remarkable growth in the urban area. The agricultural land was decreased by 11.03%, while the urban area was increased by 11.84%. The rate of agricultural land consumption by urbanization after 2001 was more remarkable than the rate before 2001. The results also indicated that the agricultural and urban land use categories have the highest possible probability of change. It is predicted that agricultural land will decrease by 11.5% and 24.5% in 2050 and 2100, respectively. Conversely, urban areas will increase by 12% and 25% in 2050 and 2100, respectively. This process will become the main feature of LULC change in the future, which means that the agricultural land could completely vanish within the next two hundred years at the current degree of agricultural land consumption by urbanization. The outcomes of this research could help policy makers to adopt appropriate strategies towards better management of LULC and increase the sustainability of the highly productive agricultural land through preventing violation on such valuable land.

Global urbanization and food production in direct competition for land: Leverage places to mitigate impacts on SDG2 and on the Earth System

Global urbanization and food production are in direct competition for land. This paper carries out a critical review of how displacing crop production from urban and peri-urban land to other areas – because of issues related to soil quality – will demand a substantially larger proportion of the Earth’s terrestrial land surface than the surface area lost to urban encroachment. Such relationships may trigger further distancing effects and unfair social-ecological teleconnections. It risks also setting in motion amplifying effects within the Earth System. In combination, such multiple stressors set the scene for food riots in cities of the Global South. Our review identifies viable leverage points on which to act in order to navigate urban expansion away from fertile croplands. We first elaborate on the political complexities in declaring urban and peri-urban lands with fertile soils as one global commons. We find that the combination of an advisory global policy aligned with regional policies enabling robust common properties rights for bottom-up actors and movements in urban and peri-urban agriculture (UPA) as multi-level leverage places to intervene. To substantiate the ability of aligning global advisory policy with regional planning, we review both past and contemporary examples where empowering local social-ecological UPA practices and circular economies have had a stimulating effect on urban resilience and helped preserve, restore, and maintain urban lands with healthy soils.

Using Very High Resolution Thermal Infrared Imagery for More Accurate Determination of the Impact of Land Cover Differences on Evapotranspiration in an Irrigated Agricultural Area

Land cover has a strong effect on the evapotranspiration (ET) and the hydrologic cycle. Urbanization alters the land cover affecting the surface energy balance and ET by, for example, urban encroachment in agricultural areas. This study investigates the potential utility of high resolution ET in determining more accurately the impact of land cover on water use for an agricultural area. The approach was to apply the physically based two-source energy balance (TSEB) model to very high resolution (~8 m) aircraft thermal data and compare the ET pattern and distribution to TSEB output using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data acquired on 2 August 2012. Modeled flux components were validated using measurements collected from a network of 16 eddy covariance (EC) towers at the study site. The modeled ET using the aircraft data agreed satisfactorily with the flux tower measurements and had better performance than the TSEB model applied to the ASTER data. The percent errors between ET closed by the Bowen ratio (BR) and residual (RE) approaches were 3 and 1%, respectively. It is shown that the high resolution aircraft ET can more accurately determine the change in ET magnitude by having pure pixels of the main land cover types, namely urban, agriculture, and natural vegetation. As a result, the ET histogram exhibits a significant bi-modal distribution which can be used to accurately distinguish the impact on ET from urban versus agricultural land cover areas and potentially monitor the effect on ET over a landscape due to small changes in land cover. At the coarser 90 m resolution of ASTER, the TSEB ET estimates are more often a combination of urban and agricultural land cover ET near the urban-agriculture land cover boundaries. As a result, the bi-modal distribution in ET is almost nonexistent. This study demonstrates the potential utility of high resolution ET mapping for more accurately determining the magnitude of the ET differences between cropland and urban land cover. It also suggests that, with high resolution thermal imagery, TSEB is a potential tool for monitoring the impact on ET due to relatively small changes in land cover as a result of urban expansion. Such a tool would be useful for watershed management.

A New Framework for Modelling and Monitoring the Conversion of Cultivated Land to Built-up Land Based on a Hierarchical Hidden Semi-Markov Model Using Satellite Image Time Series

Large amounts of farmland loss caused by urban expansion has been a severe global environmental problem. Therefore, monitoring urban encroachment upon farmland is a global issue. In this study, we propose a novel framework for modelling and monitoring the conversion of cultivated land to built-up land using a satellite image time series (SITS). The land-cover change process is modelled by a two-level hierarchical hidden semi-Markov model, which is composed of two Markov chains with hierarchical relationships. The upper chain represents annual land-cover dynamics, and the lower chain encodes the vegetation phenological patterns of each land-cover type. This kind of architecture enables us to represent the multilevel semantic information of SITS at different time scales. Specifically, intra-annual series reflect phenological differences and inter-annual series reflect land-cover dynamics. In this way, we can take advantage of the temporal information contained in the entire time series as well as the prior knowledge of land cover conversion to identify where and when changes occur. As a case study, we applied the proposed method for mapping annual, long-term urban-induced farmland loss from Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) time series in the Jing-Jin-Tang district, China from 2001 to 2010. The accuracy assessment showed that the proposed method was accurate for detecting conversions from cultivated land to built-up land, with the overall accuracy of 97.72% in the spatial domain and the temporal accuracy of 74.60%. The experimental results demonstrated the superiority of the proposed method in comparison with other state-of-the-art algorithms. In addition, the spatial-temporal patterns of urban expansion revealed in this study are consistent with the findings of previous studies, which also confirms the effectiveness of the proposed method.

Modeling Urban Encroachment on the Agricultural Land of the Eastern Nile Delta Using Remote Sensing and a GIS-Based Markov Chain Model

Historically, the Nile Delta has played an integral part in Egyptian civilization, as its fertile soils have been cultivated for centuries. The region offers a lush oasis among the expansive arid climate of Northern Africa; however, in recent decades, many anthropogenic changes to the environment have jeopardized Egypt’s agricultural productivity. Political instability and lack of sufficient regulations regarding urban growth and encroachment have put agricultural land in the area at risk. Advanced geospatial techniques were used to assess the rate at which urban areas are increasing within the region. A hybrid classification of Landsat satellite imagery for the eastern sector of the Nile Delta, between the years 1988 and 2017, was conducted to map major land-use and land-cover (LULC) classes. The statistical change analysis revealed that urban areas increased by 222.5% over the study period (29 years). Results indicated that urban areas are encroaching mainly on established agricultural lands within the Nile Delta. Most of the change has occurred within the past nine years, where approximately 235.60 km2 of the cultivated lands were transitioned to urban. Nonetheless, at the eastern delta flank, which is bordered by desert, analysis indicated that agricultural lands have experienced a considerable growth throughout the study period due to a major desert reclamation effort. Areas most at risk from future urban expansion were identified. A simulation of future urban expansion, using a Markov Chain algorithm, indicated that the extent to which urban area is simulated to grow in the region is 16.67% (277.3 km2) and 37.82% (843 km2) by the year 2026, and 2050, respectively. The methods used in this study are useful in assessing the rate of urban encroachment on agricultural lands and can be applied to similar at-risk areas in the regions if appropriate site-specific modifications are considered.

Adapting to sea level rise: Emerging governance issues in the San Francisco Bay Region

San Francisco Bay, the largest estuary on the Pacific Coast of North America, is heavily encroached by a metropolitan region with over 7 million inhabitants. Urban development and infrastructure, much of which built over landfill and at the cost of former baylands, were placed at very low elevations. Sea level rise (SLR) poses a formidable challenge to these highly exposed urban areas and already stressed natural systems.“Green”, or ecosystem-based, adaptation is already on the way around the Bay. Large scale wetland restoration projects have already been concluded, and further action now often requires articulation with the reinforcement of flood defense structures, given the level of urban encroachment. While levee setback, or removal, would provide greater environmental benefit, the need to protect urban areas and infrastructure has led to the trial of ingenious solutions for promoting wetland resilience while upgrading the level of protection provided by levees.We analyzed the region’s environmental governance and planning structure, through direct observation, interviews with stakeholders, and study of planning documents and projects. We present two examples where actual implementation of SLR adaptation has led, or may lead to, the need to revise standards and practices or require uneasy choices between conflicting public interests.Among the region’s stakeholders, there is an increasing awareness of the risks related to SLR, but the institutional arrangements are complex, and communication between the different public agencies/departments is not always as streamlined as it could be. Some agencies and departments need to adapt their procedures in order to remove institutional barriers to adaptation, but path dependence is an obstacle. There is evidence that more frank and regular communication between public actors is needed. It also emphasizes the benefits of a coordination of efforts and strategies, something that was eroded in the transition from central-government-led policies to a new paradigm of local-based adaptive governance.

Sediment starvation destroys New York City marshes’ resistance to sea level rise

New York City (NYC) is representative of many vulnerable coastal urban populations, infrastructures, and economies threatened by global sea level rise. The steady loss of marshes in NYC's Jamaica Bay is typical of many urban estuaries worldwide. Essential to the restoration and preservation of these key wetlands is an understanding of their sedimentation. Here we present a reconstruction of the history of mineral and organic sediment fluxes in Jamaica Bay marshes over three centuries, using a combination of density measurements and a detailed accretion model. Accretion rate is calculated using historical land use and pollution markers, through a wide variety of sediment core analyses including geochemical, isotopic, and paleobotanical analyses. We find that, since 1800 CE, urban development dramatically reduced the input of marsh-stabilizing mineral sediment. However, as mineral flux decreased, organic matter flux increased. While this organic accumulation increase allowed vertical accumulation to outpace sea level, reduced mineral content causes structural weakness and edge failure. Marsh integrity now requires mineral sediment addition to both marshes and subsurface channels and borrow pits, a solution applicable to drowning estuaries worldwide. Integration of marsh mineral/organic accretion history with modeling provides parameters for marsh preservation at specific locales with sea level rise.