Mapping Invasive Plant Distributions in the Florida Everglades Using the Digital Aerial Sketch Mapping Technique

Abstract The management of exotic, invasive plants is among the most challenging undertakings of natural resource managers, particularly in large, remote landscapes. The availability of information on the distribution and abundance of invasive plants is vital for effective strategic planning yet is often unavailable because of high costs and long procurement times. This paper presents results of a large-scale invasive plant mapping effort in the Florida Everglades utilizing digital aerial sketch mapping (DASM) and evaluates its utility for guiding management decisions. The distribution and abundance (cover) of four priority invasive plant species—Australian pine, Brazilian pepper, melaleuca, and Old World climbing fern—were mapped over 728,000 ha in the Everglades during 2010 to 2012. Brazilian peppertree was the most widely distributed and abundant species, occupying 30,379 ha. Melaleuca was also widely distributed and occupied 17,802 ha. Old World climbing fern occupied only 7,033 ha but its distribution was generally concentrated in heavy infestations in the northern Everglades. Australian pine was the least abundant of the mapped species and tended to be limited to the southeastern Everglades region. DASM proved to be a cost-effective means of obtaining region-wide distribution and abundance information for these species at broad scales (> 500 m), but detection rates and positional accuracy declined at finer scales. Both canopy type (forested vs. unforested) and distance from flight transect appear to be important factors for detection accuracy. Nomenclature: Australian-pine, Casuarina equisetifolia L. ex J.R. & G. Forst. , Brazilian peppertree, Schinus terebinthifolius Raddi, melaleuca, Melaleuca quinquenervia (Cav.) Blake, Old World climbing fern, Lygodium microphyllum (Cav.) R. Br. Management Implications: Spatially-explicit information on the distribution and abundance of invasive plant species is an important resource for land managers seeking to implement and assess invasive plant management programs. Obtaining such data for large landscapes is often cost-prohibitive, especially with continued decreases in operating budgets. This paper highlights the use of digital aerial sketch mapping (DASM) for collecting spatial information on invasive tree, shrub, and vine species across a vast and difficult to access wilderness—the Florida Everglades. Using specialized software on touchpad computers linked to global positioning system receivers, observers mapped infestations of four regionally significant invasive plant species—Australian-pine (Casuarina equisetifolia), Brazilian peppertree (Schinus terebinthifolius), melaleuca (Melaleuca quinquenervia), and Old World climbing fern (Lygodium microphyllum)—from low flying aircraft over a 728,000 ha region. DASM resulted in relatively rapid (roughly 10,000 ha/hr) and inexpensive ($0.11 ha-1) collection of landscape level distribution and abundance data for these species. Data validation results indicate that trained observers were able to discern the four target species across a variety of ground conditions and accurately digitize the infestations “on-the-fly. ” However, detection of small and widely scattered individuals was inconsistent, indicating limited usefulness of this technique for early detection of low-level infestations, especially in the sub-canopy of forested plant communities. Thus, DASM provided a practical and cost-efficient means for identifying the spatial extent and abundance of larger individuals and patches of the targeted species in the vast Everglades landscape. Access to this data enables land managers to more effectively plan invasive plant management strategies as well as to prioritize locations for supplemental monitoring aimed at early detection of incipient populations.