Addressing the need for improved land cover map products for policy support

The continued increase of anthropogenic pressure on the Earth’s ecosystems is degrading the natural environment and then decreasing the services it provides to humans. The type, quantity, and quality of many of those services are directly connected to land cover, yet competing demands for land continue to drive rapid land cover change, affecting ecosystem services. Accurate and updated land cover information is thus more important than ever, however, despite its importance, the needs of many users remain only partially attended. A key underlying reason for this is that user needs vary widely, since most current products – and there are many available – are produced for a specific type of end user, for example the climate modelling community. With this in mind we focus on the need for flexible, automated processing approaches that support on-demand, customized land cover products at various scales. Although land cover processing systems are gradually evolving in this direction there is much more to do and several important challenges must be addressed, including high quality reference data for training and validation and even better access to satellite data. Here, we 1) present a generic system architecture that we suggest land cover production systems evolve towards, 2) discuss the challenges involved, and 3) propose a step forward. Flexible systems that can generate on-demand products that match users’ specific needs would fundamentally change the relationship between users and land cover products – requiring more government support to make these systems a reality

Evaluation of ESA CCI prototype land cover map at 20m

In September 2017, the ESA CCI Land Cover Team released a prototype land cover (LC) map at 20 m resolution over Africa for the year 2016. This is the first LC map produced at such a high resolution covering an entire continent for the year 2016. To help improve the quality of this product, we have assessed its overall accuracy and identified regions where the map should be improved. We have compared the product against two independent datasets developed within the Copernicus Global Land Services (CGLS): a reference land cover dataset at a 10 m resolution, which has been used as training data to produce the LC map at 100 m over Africa for the year 2015 (http://land.copernicus.eu/global/products/lc); and an independent validation dataset at a 10 m resolution, which has been developed by CGLS for independent assessment of land cover maps at resolutions finer than 100 m. According to our estimates, overall accuracy of the African CCI LC at 20 m is approximately 65%. We have highlighted regions where the spatial distribution of such classes as shrubs, crops and trees should be improved before the map at 20 m could be used as input for research questions, e.g. conservation of biodiversity, crop monitoring and climate modelling

Integrating global land cover datasets for deriving user-specific maps

Global scale land cover (LC) mapping has interested many researchers over the last two decades as it is an input data source for various applications. Current global land cover (GLC) maps often do not meet the accuracy and thematic requirements of specific users. This study aimed to create an improved GLC map by integrating available GLC maps and reference datasets. We also address the thematic requirements of multiple users by demonstrating a concept of producing GLC maps with user-specific legends. We used a regression kriging method to integrate Globcover-2009, LC-CCI-2010, MODIS-2010 and Globeland30 maps and several publicly available GLC reference datasets. Overall correspondence of the integrated GLC map with reference LC was 80% based on 10-fold cross-validation using 24,681 sample sites. This is globally 10% and regionally 6–13% higher than the input map correspondences. Based on LC class presence probability maps, expected LC proportion maps at coarser resolution were created and used for characterizing mosaic classes for land system modelling and biodiversity assessments. Since more reference datasets are becoming freely accessible, GLC mapping can be further improved by using the pool of all available reference datasets. LC proportion information allow tuning LC products to specific user needs.</p

Land cover harmonization using Latent Dirichlet Allocation

Large-area land cover maps are produced to satisfy different information needs. Land cover maps having partial or complete spatial and/or temporal overlap, different legends, and varying accuracies for similar classes, are increasingly common. To address these concerns and combine two 30-m resolution land cover products, we implemented a harmonization procedure using a Latent Dirichlet Allocation (LDA) model. The LDA model used regionalized class co-occurrences from multiple maps to generate a harmonized class label for each pixel by statistically characterizing land attributes from the class co-occurrences. We evaluated multiple harmonization approaches: using the LDA model alone and in combination with more commonly used information sources for harmonization (i.e. error matrices and semantic affinity scores). The results were compared with the benchmark maps generated using simple legend crosswalks and showed that using LDA outputs with error matrices performed better and increased harmonized map overall accuracy by 6–19% for areas of disagreement between the source maps. Our results revealed the importance of error matrices to harmonization, since excluding error matrices reduced overall accuracy by 4–20%. The LDA-based harmonization approach demonstrated in this paper is quantitative, transparent, portable, and efficient at leveraging the strengths of multiple land cover maps over large areas

Developing and applying a multi-purpose land cover validation dataset for Africa

The production of global land cover products has accelerated significantly over the past decade thanks to the availability of higher spatial and temporal resolution satellite data and increased computation capabilities. The quality of these products should be assessed according to internationally promoted requirements e.g., by the Committee on Earth Observation Systems-Working Group on Calibration and Validation (CEOS-WGCV) and updated accuracy should be provided with new releases (Stage-4 validation). Providing updated accuracies for the yearly maps would require considerable effort for collecting validation datasets. To save time and effort on data collection, validation datasets should be designed to suit multiple map assessments and should be easily adjustable for a timely validation of new releases of land cover products. This study introduces a validation dataset aimed to facilitate multi-purpose assessments and its applicability is demonstrated in three different assessments focusing on validating discrete and fractional land cover maps, map comparison and user-oriented map assessments. The validation dataset is generated primarily to validate the newly released 100 m spatial resolution land cover product from the Copernicus Global Land Service (CGLS-LC100). The validation dataset includes 3617 sample sites in Africa based on stratified sampling. Each site corresponds to an area of 100 m × 100 m. Within site, reference land cover information was collected at 100 subpixels of 10 m × 10 m allowing the land cover information to be suitable for different resolution and legends. Firstly, using this dataset, we validated both the discrete and fractional land cover layers of the CGLS-LC100 product. The CGLS-LC100 discrete map was found to have an overall accuracy of 74.6 ± 2.1% (at 95% confidence level) for the African continent. Fraction cover products were found to have mean absolute errors of 9.3, 8.8, 16.2, and 6.5% for trees, shrubs, herbaceous vegetation and bare ground, respectively. Secondly, for user-oriented map assessment, we assessed the accuracy of the CGLS-LC100 map from four user groups' perspectives (forest monitoring, crop monitoring, biodiversity and climate modelling). Overall accuracies for these perspectives vary between 73.7% ± 2.1% and 93.5% ± 0.9%, depending on the land cover classes of interest. Thirdly, for map comparison, we assessed the accuracy of the Globeland30-2010 map at 30 m spatial resolution. Using the subpixel level validation data, we derived 15,252 sample pixels at 30 m spatial resolution. Based on these sample pixels, the overall accuracy of the Globeland30-2010 map was found to be 66.6 ± 2.4% for Africa. The three assessments exemplify the applicability of multi-purpose validation datasets which are recommended to increase map validation efficiency and consistency. Assessments of subsequent yearly maps can be conducted by augmenting or updating the dataset with sample sites in identified change areas

Dinámica, modelización y servicios ecosistémicos del paisaje. Metodología para el análisis de la franja costera del Mediterráneo occidental

El análisis y la dinámica de los paisajes a lo largo del tiempo y el espacio es esencial para la caracterización, ordenación y gestión de los paisajes actuales. Los paisajes, entendidos en su amplia escala espacial y temporal, son una expresión del trabajo conjunto de la naturaleza y el ser humano y por tanto un recurso territorial, un patrimonio y una señal de identidad, que necesita atención, protección y gestión. En el Convenio Europeo del Paisaje se institucionaliza el interés y el derecho al paisaje, y se insta a que los estados y regiones firmantes articulen políticas de paisaje en el marco de la ordenación territorial. Políticas que se operativizan mediante la identificación, análisis y caracterización de los paisajes presentes, así; como de sus dinámicas y los factores que contribuyen al cambio.Este conocimiento es la base sobre la que se fundamenta la toma de decisiones en la intervención en el territorio; en la manera de proteger, de ordenar o de gestionar los paisajes y en el modo de plantear el planeamiento. Para apoyar esa toma de decisiones se necesita disponer de un conocimiento profundo de los componentes, procesos, relaciones e interpretaciones que explican el carácter de cada paisaje. Es necesario identificar cuáles son los tipos de paisaje y las unidades de paisaje; conocer la dinámica histórica y además, disponer de un modelo geoespacial que nos permita generar los escenarios futuros según las diferentes decisiones previstas. Esta dinámica espacio-temporal, junto con los escenarios de futuro previstos influyen decisivamente sobre el capital natural y cultural de un territorio. En este sentido, la dinámica de los paisajes genera cambios en los servicios ecosistémicos y en el sentido de lugar, que es necesario evaluar. Las áreas periurbanas de la franja litoral del Mediterráneo occidental han experimentado una fuerte transformación, debido a la histórica e intensa ocupación humana del litoral. El objetivo de este trabajo es proponer una metodología que explique la transformación del paisaje en espacios litorales, tanto en su dinámica histórica como los posibles escenarios de futuro. Además, se pretende evaluar la influencia del cambio en el paisaje sobre los servicios ecosistémicos, tomando como áreas de estudio el municipio de Castelló de la Plana y el Área Metropolitana de Valencia. La finalidad es identificar y comprender la manera en que la sociedad se ha apropiado y ha ocupado la franja litoral, generando unas nuevas dinámicas territoriales y jerarquías espaciales. La investigación busca desarrollar la metodología y las técnicas de análisis geográfico, que permitan explicitar los elementos motores en la evolución del paisaje, su transformación y las consecuencias sobre los servicios ecosistémicos.Landscape is a human construction in continuous process of change. The methodology proposed to analyse the landscape dynamics is based on landscape diachronic study. Documentary availability (cartography, orthophotography, aerial photography, oblique, etc.), geographic information systems (GIS) and geospatial modelling are the criteria established to mark the different stages of analysis within the time series. For this, land cover information is used to identify landscape patterns for a later stage, incorporating the physiographic, lithological and biometric models to obtain landscape types for the entire time series. With the defined landscape types, landscape units are geographically mapped and delimited with the support of orthophotography, aerial photographs and historical cartographies, as well as historical documentation. This methodological procedure is performed for the two study areas, with two spatial scales (local and supralocal) and two different time scales (30 and 105 years). All this to obtain patterns of change in dynamics of cultural landscape over time and space, both quantitative and spatial variation and fragmentation that allow us to explain the current landscape situation. We obtain a dynamic of constant growth of urban landscape types, a sustained maintenance of the irrigation agricultural types and a marked decrease of the rain feed agricultural types. Finally, forest types have a tendency of slight growth and marsh types, wetland and rice fields disappear into the area A1, Castelló de la Plana, or reduce its importance in the area A2, metropolitan area of Valencia. With all this, we obtain a steady increase in the fragmentation of landscape units. Along with the methodology for obtaining the historical landscape dynamics, it is also proposed to analyse the possible future scenarios according to the decision-making process. To do this, a geospatial model is generated by using the Dinamica EGO software; along stochastic processes, Markov chain and cellular automata (CA). In this model, previously delimited and mapped landscape types and units are used as input data, and spatial variables that induce change as Weight of Evidence. Transition matrices are obtained, variables that induce the change in ranges and coefficients are categorized and geospatial model is calibrated. The various iterations of the calibration are validated for quality, in order to achieve finer calibration that will be used for simulation. Scenario generation is carried out with the geospatial model calibrated by adjusting variables according to the tendency to be analysed. In our research we generate two scenarios, of continuity and change, for area A1, Castelló de la Plana, and a scenario of continuity for area A2, metropolitan area of Valencia. The scenarios modelled trends maintain the landscape dynamics, except for irrigation agricultural types passing from peacekeeping to moderate reduction. As for fragmentation it continues to increase in all scenarios, but on scenario 2, area A1 Castelló de la Plana, its increase is significantly reduced. Finally, we propose a methodology to analyse the evolution of ecosystem services and their relationship with landscape dynamics and its different scenarios. We use two attributes of the soil on the landscape units: soil use capacity and soil water storage capacity. Through these attributes we are evaluating provisioning services, related to food production, and regulation and supporting services, related to water supply, food production and support of ecosystem processes. We obtain a generalized loss of both ecosystem services over the time series and scenarios. This may be limited by taking into consideration ecosystem services and incorporating them into decision-making when generating scenarios