The rapid expansion of Lantana camara in areas outside of its natural habitat (originally the American tropical zone) has resulted in its spread across 20 million acres. The Biligiri Ranganathaswamy Hills Tiger Reserve is located in Southern Peninsular India. We have examined the reach of this shrub in dense thorny thickets all over the park. It has smothered other species of plants and blocked the flow of wildlife, posing a huge problem for the park’s managers.
Lantana Camara isn’t unique in its impact. Other extinct species include the famous salt cedar, which is found in Eurasia and has altered vast landscapes due to its rapid spread in just several years.
Conservation planners, like the directors of the Biligiri Ranganathaswamy reserve, consider it challenging to limit the accelerated growth of extinct alien species, which affects local biodiversity as well as ecological services.
The most aggressive of the invaders, like Lantana camara, either completely or partially substitute for the native species of shrubs in the forests. Lantana was initially introduced to be used as an ornamental plant and has since spread widely because of the feeding of birds on berries and other invasive species, such as Chromolaena or odorata (sunflower family), which are dispensed by wind.
Monitoring the invaders
It is essential to find solutions that offer high-quality, regularly up-to-date maps showing the location of invasive plants in order for them to be identified, targeted, and eliminated. Due to the vast areas they cover, the authorities tend to turn to more and more advanced methods like remote sensors.
It involves taking pictures of landscapes using specially designed cameras in space (on satellites) or in the air (on aircraft), which recognize more than what human eyes can detect, for instance, due to their ability to capture information within the infrared and thermal visible spectrum and then obtaining details from these photos.
In recent years, extremely high-resolution satellite images have been made available. They are able to detect objects smaller than a meter. They are able to differentiate between plants because of pictures taken in very narrow, highly precise wavelengths of the electromagnetic spectrum.
We looked at recent studies in this direction. We found that although technological advances are beneficial, they need to be coupled with an ecological understanding of the behavior of plants that are invasive to provide more efficient mapping.
Functional traits of plants are a powerful method of capturing the most important characteristics of invasive species. These traits can be used to map using satellites. Plant traits are the characteristics of the plant’s function and structure that affect the way they spread, live, and adapt to environmental conditions and others. Of the numerous characteristics plants possess, some are suited for mapping with satellite data. They can be categorized into three kinds, namely seasonal (phenological) and structural physiological.
Invasive Lantana camara occupies niches in the sub storey tropical forest. Madhura Niphadkar (Author) supplied
Seasonal variations
The plants produce seeds, leaves, and flowers at certain seasons and can be monitored through remote sensors. There are differences between invasive species and native species during the onset of senescence (colored leaves and leaf autumn) or leaves (green leaves), and flowering (presence of flowers that are colored) are evident within the specific wavelengths that satellite sensors use at particular dates during the season.
This is a particularly effective method to map plants and plants that are found in the lower part of the canopy and are not visible to satellite sensors. For example, the pest Amur honeysuckle Lonicera Mackiei was identified in late autumn/autumn, which was when the deciduous plants were unfurled, and the invasive climber was easily apparent through the gaps in leaves of the overstorey tree.
Amur honeysuckle is the understorey climber. Fanghong/Wikimedia, CC BY-NC
The physiological and structural aspects
Structural characteristics – like clusters of plants clumping together, scattered among native plants, or the height of a plant – can be effectively used to map. In our studies at the Biligiri Ranganathaswamy Reserve, We could trace the Lantana camera’s huge contiguous clumps that spread patterns. LIDAR Data, which utilizes pulsed laser light beams to give 3D maps of the surface of the earth, can be useful, for example, to study the distribution of five invasive species of trees that are found in Hawaiian woodlands.
