Monitoring the Invasion ofSpartina alternifloraUsing Very High Resolution Unmanned Aerial Vehicle Imagery in Beihai, Guangxi (China)

Abstract

Spartina alterniflora was introduced to Beihai, Guangxi (China), for ecological engineering purposes in 1979. However, the exceptional adaptability and reproductive ability of this species have led to its extensive dispersal into other habitats, where it has had a negative impact on native species and threatens the local mangrove and mudflat ecosystems. To obtain the distribution and spread of Spartina alterniflora, we collected HJ-1 CCD imagery from 2009 and 2011 and very high resolution (VHR) imagery from the unmanned aerial vehicle (UAV). The invasion area of Spartina alterniflora was 357.2 ha in 2011, which increased by 19.07% compared with the area in 2009. A field survey was conducted for verification and the total accuracy was 94.0%. The results of this paper show that VHR imagery can provide details on distribution, progress, and early detection of Spartina alterniflora invasion. OBIA, object based image analysis for remote sensing (RS) detection method, can enable control measures to be more effective, accurate, and less expensive than a field survey of the invasive population.

Object-Based Image Analysis in Wetland Research: A Review

“…These included peer-reviewed journal articles, conference papers and chapters of book and PhD thesis publications. This review specifically focused on vegetated wetlands (i.e., colonized by aquatic macrophytes) of diverse types [36] such as fresh-and salt-water estuarine, riverine, lacustrine, palustrine and selected marine (mangrove) ecosystems (Table 1, [5][6][7][8]12,13,[15][16][17][18][22][23][24][25][26][27][28][29][30]32,34,) and excluded studies of solely deepwater and open-water aquatic ecosystems such as seagrass beds. The OBIA applications and main research objectives fell into several broad groups (with some papers applicable to more than one of these):…”

“…Typological classification of delineated wetland units: assignment of mapped wetland bodies into hydrological, geomorphological and ecological categories without detailed mapping of within-wetland cover [6,27,29,37,43,44,55,65,66,73,79,80]; (3). Classification of within-wetland cover types and/or vegetation: mapping within-wetland surface composition and vegetation types, sometimes targeting specific classes such as invasive plant species (e.g., [5,8,12,13,17,[23][24][25]28,30,32,34,41,45,[48][49][50]52,53,57,68,69,[74][75][76][77][79][80][81][82][83][84][85]); (4). Analysis of wetland change over a particular period of time...…”

“…Among previously published literature reviews, those focusing on OBIA progress have predominantly included studies from non-wetland landscapes [20,31], while the reviews of remote sensing applications in wetlands [9][10][11] have not aimed at detailed discussions of OBIA-specific issues. Thus, the time for a targeted synthesis of the OBIA progress and challenges in wetlands is ripe given the demand for novel OBIA applications in wetland restoration projects and exotic species monitoring [3,8,32] and the growing use of high-and very-high resolution imagery from new remote sensing platforms such as UAVs [33][34][35]. New insights about technical and conceptual limitations of OBIA in wetlands [28] also highlight the urgent need to better understand the nature of present constraints and develop solutions in the future research efforts.…”

Open-Source Processing and Analysis of Aerial Imagery Acquired with a Low-Cost Unmanned Aerial System to Support Invasive Plant Management

“…In general, this approach can allow environmental managers to monitor the distribution and spread of invasive plants in similar situations once the classification models are adjusted to the respective species. Environmental managers should be strongly encouraged to use low-cost UAS approaches to avoid high costs and timeconsuming field surveys, especially in sites of low accessibility (Wan et al, 2014;Chabot et al, 2016;Hill et al, 2016;Müllerová et al, 2017). Minimizing in situ mapping and control operations is also an added advantage for using UAS, because reduction in habitat disturbance can encourage the recovery of native plants that are threatened by biological invasion (Mack and D'Antonio, 1998;Huston, 2004).…”

“…Unmanned Aerial Systems (UAS), popularly known as drones, introduce a new remote sensing technique that may become an applicable and affordable alternative to conventional approaches, as they reduce costs and increase the spatial resolution of aerial images (Wan et al, 2014;Dvořák et al, 2015;Chabot et al, 2016;Hill et al, 2016;Müllerová et al, 2016Müllerová et al, , 2017. The technical development, component miniaturization, and increased sales in recent years resulted in the rapid growth of UAS as an environmental remote-sensing platform.…”