Waterfowl surveys, especially for endangered waterfowl living in wetlands, are essential to protect endangered waterfowl and to create a management scenario of their habitats. Unmanned aerial vehicles (UAVs) are powerful new tools for waterfowl surveys. In this paper, we propose one method for a habitat survey and another for a waterfowl species distribution survey. The habitat survey method obtained the waterfowl’s habitat and spatial distribution with a UAV automatic flight plan in the aggregation area. The waterfowl species distribution survey was used to detect and identify waterfowl species with high-spatial-resolution images from a free UAV flight plan in the aggregation area or areas where individuals were suspected to be present. The UAV-based data showed not only the area where waterfowl were found, but also additional ground surveys. The results showed that the species and locations of the waterfowl were recorded more accurately and efficiently using the distribution method based on the images from the UAV. The waterfowl habitat type and the number of waterfowl were obtained in detail using the habitat survey method. UAV-derived counts of waterfowl were greater (+37%) than ground counts. The results indicated the feasibility and advantages of using a low-cost UAV survey of large waterfowl in wetland regions with complex vegetation. This study provides one case study of large waterfowl numbers and habitat surveys. The UAV-based methods also provide a feasible and scientific way to obtain basic data for the protection and management of waterfowl.
This is a research on the change of nutrients and its structure in the Pearl River Estuary by the principal component analysis (PCA) according to the data and materials on water quality observation in the last 30 years around the Pearl River Estuary. Results showed that inorganic nitrogen (DIN) presented an obvious increase trend in the last 30 years, while phosphate and silicate presented an outstanding decrease trend in this area by the influence of human activities. The average N/P ratio increased by 1.44 times, the Si/N ratio decreased by 66.8%, the Si/P ratio decreased by 18.5%, and the structure of nutrients changed significantly. According to the results of PCA, the first two principal components (PC) were extracted. PC1 was associated with GDP, population, industrial output value and wastewater discharge, which explained 80.9% of the variance. PC2 was characterized by cultivated land area, which explained 14.6% of the variance. It indicates that the change of nutrients content and structure in the Pearl River Estuary was closely related to economic development and industrial pollution discharge, and the effect of the change of land use and land cover on the change of nutrients should not be ignored.
Based on the InVEST model, the spatial and temporal evolution trends of water and soil conservation service functions in northern Guangdong in the three periods from 2000 to 2018 were evaluated, and the factors affecting the changes and spatial distribution of soil conservation time were further analyzed. The results indicate: (1) The average soil erosion per unit area in the study area in different years is 5.9∼7.6 t/ha•a, 81∼87% of the study area is mild erosion. (2) The amount of soil retention per unit area in the study area increased firstly and then decreased, reaching a maximum of 68.87 t/ha•a in 2010. This change was mainly caused by the difference in rainfall erosivity caused by precipitation. (3) The low-value areas of soil retention in the study area are mainly distributed in the central urban areas of Shaoguan, Qingyuan, Nanxiong Basin and Wengjiang Basin. The high-value areas are mainly distributed in the mountainous areas, such as Dadong Mountain, Qiweishan Mountain, Luoke Mountain, Huashui and Huangsi-nao Mountain. (4) The main factors affecting the spatial difference of soil retention in the study area are land use type, altitude, and slope. Under different land use types, the amount of soil retention per unit area from large to small is woodland> grassland> water area> cultivated land> construction land.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.