Temperate Grassland Afforestation Dynamics in the Aguapey Valuable Grassland Area between 1999 and 2020:Identifying the Need for Protection

Temperate grasslands are considered the most endangered terrestrial ecosystem worldwide; the existent areas play a key role in biodiversity conservation. The Aguapey Valuable Grassland Area (VGA), one of the most well-preserved temperate grassland areas within Argentina, is currently threatened by the anthropogenic expansion of exotic tree plantations. Little is known about the impacts of afforestation over temperate grassland landscape structures; therefore, the aim of this study is to characterize Aguapey VGA landscape structural changes between 1999 and 2020 based on remotely sensed data. This involves the generation of land cover maps for four annual periods based on unsupervised classification of Landsat 5 TM and 8 OLI images, the estimation of landscape metrics, and the transition analysis between land cover types and annual periods. The area covered by temperate grassland is shown to have decreased by almost 22% over the 20 year-period studied, due to the expansion of tree plantation cover. The afforestation process took place mainly between 1999 and 2007 in the northern region of the Aguapey VGA, which led first to grassland perforation and subsequently to grassland attrition; however, Aguapey’s cultural tradition of cattle ranching could have partially inhibited the expansion of exotic trees over the final years of the study. The evidence of grassland loss and fragmentation within the Aguapey VGA should be considered as an early warning to promote the development of sustainable land use policies, mainly focused towards the Aguapey VGA’s southern region where temperate grassland remains the predominant land cover type

Sussex coastal habitats inshore pilot II: Marine habitat and bathymetry modelling

The Sussex Coastal Habitats Inshore Pilot (SCHIP) 2 project follows on from the preceding SCHIP 1 project, which was led by the Sussex Inshore Fisheries and Conservation Authority (IFCA), working in partnership with Sussex Wildlife Trust, and funded by the Environment Agency. The project aims to explore and analyse existing sea floor habitat and bathymetric data sets available for the Sussex IFCA district. These data are used to construct both a broad scale habitat model classified to European Nature Information System (EUNIS) level 3 and a detailed fine scale habitat model classified up to EUNIS level 6. In addition, a bathymetric model of the entire district is produced from survey data taken by IFCA’s patrol and research vessel ‘Watchful’. Four existing seabed habitat data sets (EUNIS Sussex 2010, JNCC UK Sea Map 2010, EUNIS South East, and RoxAnn) were converted into a single layer containing the features and attributes of all four individual shape files. EUNIS habitat values from all four polygon data sets were compared using a four way comparison of column values, and returned the number of matching values. This was carried out to compare all four data sets, and to provide a final layer which showed the level of agreement between layers and described the extent of known seabed habitats to EUNIS level 3. In order to create a finer-scale and continuous EUNIS habitat layer a Voronoi polygon method was developed and used. Voronoi polygons are presented as an independent method by which to convert point data into a polygon coverage and to divide up the seabed into EUNIS habitat codes. Within each voronoi polygon, any given location contained is closer to the known point in that polygon than any other known point (ESRI, 2007). All non-sampled locations are classified in accordance with the nearest known point Where survey point density is higher (more known points per unit area), smaller polygons are constructed and the data can show increased habitat variability. Areas where voronoi polygons are smaller are likely to represent seabed habitats more closely due to higher survey/point density. The predictive habitat maps suggest that A5 (sublittoral sediment) habitats are dominant throughout the district. A3 (Infralittoral rock and other hard substrata) and A4 (Circalittoral rock and other hard substrata) habitats are predicted in small areas. The EUNIS level 3 map is perhaps adequate as an indication of the overall habitat trends within this biologically significant region. However, the method has been applied up to EUNIS level 4, 5, and 6 at specified locations, where data are available, and facilitates more detailed biological interpretation at specific locations. Fine-scale seabed habitat models were validated in sample areas against contemporary MBES surveys and habitat maps to assess accuracy; validation suggested a strong associated with independent data. The study highlights the importance of citizen science data (e.g. Seasearch) in developing an increased understanding and knowledge of the habitats in this region and others throughout the UK. More developed seabed habitat maps are crucial for the success of current and future fisheries management

The use of small-Unmanned Aerial Systems for high resolution analysis for intertidal wetland restoration schemes

Coastal and estuarine wetlands provide a range of important ecosystem services, but are currently being damaged and degraded due to human activities, reduced sediment supply and sea level rise. Managed realignment (MR) is one approach used to compensate for the loss of intertidal habitat, however saltmarshes in MR sites have been recognised to have lower biodiversity than natural environments. This has been associated with differences in the physical functioning including the sediment structure, reduced hydraulic connectivity, and lower topographic variability such as the abundance of intertidal creek networks. Intertidal morphology, including creek networks, play an important role in supporting and regulating saltmarsh environments through the supply of sediment, nutrients and water, and in draining intertidal marshes. However, there is a lack of empirical data on the formation and evolution of topographic features and variability in saltmarsh environments. This is likely to be due to creek networks in natural marshes already being in a state of quasi-equilibrium, making MR sites an ideal environment to investigate creek development. However, traditional remote sensing techniques (such as LiDAR) tend to be relatively expensive, infrequent and at a coarse resolution meaning small, but important (cm-scale), changes are often missed. This study advances the ability to detect these small scale changes by demonstrating the suitability and potential applications of using the emerging photogrammetric method Structure-from-Motion (SfM) on images taken using a small-Unmanned Aerial System (sUAS). Three surveys from a rapidly changing, near-breach site were taken at the Medmerry Managed Realignment Site in July 2016, September 2017 and July 2018. A suitable degree of confidence was found between the modelled surface and independent check points (vertical root-mean-square-errors of 0.0245, 0.0704 and 0.1571 for 2016, 2017 and 2018 respectively). DSMs of Difference (DoD) analysis was performed to evaluate elevation change, with areas experiencing up to 85 cm of accretion between 2016 and 2018. However, when considering the error associated with both surveys, between 2016 and 2017, only 34.39% of the survey area experienced change above the level of detection (LoD). In contrast, 76.97% experienced change greater than the LoD between 2017 and 2018. Stream order analysis classified the creek networks into five orders in 2016 and four orders in 2017 and 2018, with 2016 having a higher abundance (291 in 2016 compared to 117 (2017) and 112 (2018)) and density (0.44 m/m2 in 2016 compared to 0.27 m/m2 in both 2017 and 2018) of creek networks. These results provide an innovative high resolution insight into the evolution of restored intertidal wetlands, and suggest that SfM analysis of images taken using a sUAS can be a useful tool with the potential to be incorporated into studies of MR and natural saltmarsh sites. sUAS analysis can, therefore, advance the management of these environments to ensure the provision of ecosystem services and to protect against future anthropogenic activity, sea level rise and climate change

The Use of Unmanned Aerial Vehicles to Determine Differences in Vegetation Cover: A Tool for Monitoring Coastal Wetland Restoration Schemes

Managed realignment (MR) sites are being implemented to compensate for the loss of natural saltmarsh habitat due to sea level rise and anthropogenic pressures. However, MR sites have been recognised to have lower morphological variability and coverage of saltmarsh vegetation than natural saltmarsh sites, which have been linked with the legacy of the historic (terrestrial) land use. This study assesses the relationship between the morphology and vegetation coverage in three separate zones, associated with the legacy of historic reclamation, of a non-engineered MR site. The site was selected due to the phased historical reclamation, and because no pre-breaching landscaping or engineering works were carried out prior to the more recent and contemporary breaching of the site. Four vegetation indices (Excess Green Index, Green Chromatic Coordinate, Green-Red Vegetation Index, and Visible Atmospherically Resistant Index) were calculated from unmanned aerial vehicle imagery; elevation, slope, and curvature surface models were calculated from a digital surface model (DSM) generated from the same imagery captured at the MR site. The imagery and DSM summarised the three zones present within the MR site and the adjacent external natural marsh, and were used to examine the site for areas of differing vegetation cover. Results indicated statistically significant differences between the vegetation indices across the three zones. Statistically significant differences in the vegetation indices were also found between the three zones and the external natural saltmarsh. However, it was only in the zone nearest the breach, and for three of the four indices, that a moderate to strong correlation was found between elevation and the vegetation indices (r = 0.53 to 0.70). This zone was also the lowest in elevation and exhibited the lowest average value for all indices. No relationship was found between the vegetation indices and either the slope or curvature in any of the zones. The approach outlined in this paper provides coastal managers with a relatively low-cost, low-field time method of assessing the areas of vegetation development in MR sites. Moreover, the findings indicate the potential importance of considering the historic morphological and sedimentological changes in the MR sites. By combining data on the areas of saltmarsh colonisation with a consideration of the site’s morphological and reclamation history, the areas likely to support saltmarsh vegetation can be remotely identified in the design of larger engineered MR sites maximising the compensation for the loss of saltmarsh habitat elsewhere