DOI: 10.5061/dryad.jq2bvq8pm
title: Data from: Vehicle-mounted cameras reveal negative impact of the Fukushima Daiichi nuclear power plant accident on large-bodied bird abundance via paddy field abandonment

description: Populations of birds utilizing farmlands are declining due to farmland
 abandonment and agricultural intensification. Effective conservation
 strategies require appropriate monitoring approaches, including efficient
 and scalable survey methods. In this study, we developed a large-scale
 monitoring method for herons and egrets (family Ardeidae, hereafter
 referred to as herons) using vehicle-mounted video cameras and distance
 sampling models that incorporate location uncertainty. The survey was
 conducted in and around the evacuation zone of the Fukushima Daiichi
 nuclear power plant accident. A total of 7031 km of roadside
 video footage was recorded, covering 24.41 km² of farmland.
 Herons were observed only outside the evacuation zone and were entirely
 absent within it. Predicted abundance differed greatly between areas
 inside (0.0279 ± 0.0307/km2) and outside
 (4.57 ± 5.36/km2) the evacuation zone. Incorporating
 location uncertainty into the distance sampling model had little effect on
 the estimates (4.57 ± 5.36 vs.
 4.51 ± 5.29/km2 with and without integrating location
 uncertainty, respectively). This finding suggests that our video-based
 roadside survey method is robust to location uncertainty in structured
 landscapes such as Japanese paddy fields. The accuracy may be attributed
 to the study system, where levees and roads divide paddy fields, limiting
 potential error in observer-target distances. Our method can be applied to
 other open habitats, including natural grasslands and wetlands, especially
 in areas lacking artificial markers, by incorporating measurement
 uncertainty into the model. This combination of roadside surveys with
 vehicle-mounted cameras and distance sampling provides a practical and
 transferable approach for monitoring large-bodied species in open
 landscapes, enhancing both the efficiency and spatial coverage of
 biodiversity assessments.
description: # Data from: Vehicle-mounted cameras reveal negative impact of the
 Fukushima Daiichi nuclear power plant accident on large-bodied bird
 abundance via paddy field abandonment Dataset DOI:
 [10.5061/dryad.jq2bvq8pm](https://doi.org/10.5061/dryad.jq2bvq8pm) ##
 Description of the data and file structure The dataset was collected by
 the authors to estimate the abundance of herons and egrets in paddy fields
 using vehicle-mounted video cameras and distance sampling models. The data
 were obtained from roadside surveys and UAV-based validation, and are used
 to model bird abundance in relation to farmland abandonment following the
 Fukushima Daiichi nuclear power plant accident.The dataset consists of the
 following three .csv files: ### Files and variables #### 1. Grid-level
 farmland data (d0.csv) **This file contains grid-level data used for
 modeling heron and egret abundance based on roadside video surveys. Each
 row represents a grid cell within a farmland polygon.** ##### Variables *
 `poly_id.x, DATE`: Polygon and survey identifiers * `x, y, X_3100,
 Y_3100`: Coordinates (decimal and UTM Zone 54N, EPSG:3100) * `HubDist`:
 Distance from the camera to the grid cell (meters) * `water`: Area of
 water bodies within the 1 km mesh (Ogawa et al. 2013) that contains the
 grid cell (standardized) * `evac`: Evacuation zone status; 1-3 indicates
 the evacuation zone, 0 indicates around the zone. The evacuation zone is
 divided into three categories according to radiation levels: Preparing for
 the Lifting of the Evacuation Order Area (1), Restricted-Residential Area
 (2), and Difficult-to-Return Area (3) * `sagi`: Presence/absence of herons
 * `area`: Area of the grid cell (km²) Note: Coordinates are based on the
 centroids of grid cells derived from farmland polygons. The geographical
 and projected coordinate systems are JGD2000 (EPSG:4612) and UTM Zone 54N
 (EPSG:3100), respectively. #### 2. Location Error Validation Data
 (dmatrix3.csv) **This file contains data used to quantify location
 uncertainty in heron observations by comparing vehicle-mounted camera
 detections with UAV-based ground truth.** ##### Variables: * `Distance`:
 Euclidean distance (meters) between the observed location (vehicle camera)
 and the true location (UAV) * `cardis`: Distance from the camera to the
 heron (meters) #### 3. Prediction Mesh Data (farm-polygon.csv) **This file
 contains mesh-level data for extrapolating heron abundance across the
 broader study area.** ##### Variables: * `pointid, grid_code, Mesh3id`:
 Grid, and mesh identifier * `X, Y`: Coordinates (decimal) * `water_std`:
 Standardized area of water bodies contained within each 1 km mesh (Ogawa
 et al. 2013) * `evac2, evac3`: Evacuation zone status (actual and
 counterfactual); 2 indicates the evacuation zone, 1 indicates around the
 zone ## Access information Area of water surfaces was derived from: Ogawa,
 M., Takenaka, A., Kadoya, T., Ishihama, F., Yamano, H., and Akasaka, M.
 (2013) Land-use classification and mapping at a whole scale of Japan based
 on a national vegetation map. Japanese Journal of Conservation Ecology
 18:69-76.