Integrating conventional classifiers with a GIS expert system to increase the accuracy of invasive species mapping

Mapping the cover of invasive species using remotely sensed data alone is challenging, because many invaders occur as mid-level canopy species or as subtle understorey species and therefore contribute little to the spectral signatures captured by passive remote sensing devices. In this study, two common non-parametric classifiers namely, the neural network and support vector machine were used to map four cover classes of the invasive shrub Lantana camara in a protected game reserve and the adjacent area under communal land management in Zimbabwe. These classifiers were each combined with a geographic information system (GIS) expert system, in order to test whether the new hybrid classifiers yielded significantly more accurate invasive species cover maps than the single classifiers. The neural network, when used on its own, mapped the cover of L. camara with an overall accuracy of 71% and a Kappa index of agreement of 0.61. When the neural network was combined with an expert system, the overall accuracy and Kappa index of agreement significantly increased to 83% and 0.77, respectively. Similarly, the support vector machine achieved an overall accuracy of 64% with a Kappa index of agreement of 0.52, whereas the hybrid support vector machine and expert system classifier achieved a significantly higher overall accuracy of 76% and a Kappa index of agreement of 0.67. These results suggest that integrating conventional image classifiers with an expert system increases the accuracy of invasive species mapping.

Research highlights▶ We test whether integrating the spectral signatures of remotely sensed data with ancillary spatial data and prior knowledge about the distribution of the target invasive species enhances the capability of conventional image classifiers to detect and map invasive plant species. ▶ Combining two widely used image classifiers namely, the neural network and support vector machine, with expert system rules in a GIS resulted in greater discrimination of four cover classes of the invasive shrub L. camara which were difficult to classify and map using remotely sensed data alone. ▶ Hybrid classifiers yield significantly more accurate invasive species cover maps than the single classifiers.