Qualitative distinction of congeneric and introgressive mangrove species in mixed patchy forest assemblages using high spatial resolution remotely sensed imagery (IKONOS)

Abstract

This paper is a preliminary report of the ability of IKONOS multispectral satellite imagery with a very high spatial resolution of 1 metre to distinguish two mangrove species in Sri Lanka belonging to the same genus (Rhizophora apiculata and R. mucronata). Not only is this an advancement for the monitoring of forests, it is even more important considering their patchy nature in Sri Lankan mangroves (in contrast to classically zoned forests). Apart from congeneric distinction, introgressive species (Acrostichum aureum) can also be detected from IKONOS imagery, which is important in the early warning for cryptic ecological changes that may affect mangrove species composition (both floral and faunal) and functioning. The results tabulate the usage of various image composites, transformations and classifications, and indicate the danger of too much detail in remote sensing, and the need to apply an optimum resolution. We also highlight that the highest resolutions (as in pansharpened multispectral composites) remain invaluable for visual ecological investigations, which are not at all outdated by new digital satellite images of (sub)metre spatial resolution and their possibility for computer-aided analysis.

Ecosystem-Wide Impacts of Deforestation in Mangroves: The Urabá Gulf (Colombian Caribbean) Case Study

“…No correlation was observed between the selective logging of A. germinans and the IVI of L. racemosa in basin mangroves, contrary to the observed in Belizean [64] and Puerto Rican [66] mangroves. In the surroundings of Turbo City (Punta Las Vacas), the mangrove fern Acrostichum aureum also invaded extensively cleared fringing mangroves (Figure 4(l)), and it has become a major barrier for natural recovery, as observed elsewhere [8,25,46,67]. In other areas such as Punta Yarumal where mangrove trees have been selectively logged, A. aureum formed clumps in the understory.…”

“…Therefore, it is important to understand the objectives of selective logging to explain patterns in terms of sizes exploited, level of exploitation, degree of mechanization, and spatial distribution as influenced by access from towns and villages [6,25,32]. Although ethnoecological studies have been instrumental for reconstruction of past uses of mangroves and impacts derived [8,46,47,54], more studies are urged for the Neotropics because a few case studies exist (e.g., Mexico: [55], Venezuela: [53]) and most of the examples concentrate in the Indopacific [6].…”

“…Provisioning services are the most commonly appreciated and include sources of timber, fibers and nonwoody products, fuels (firewood and charcoal), food (fisheries), biochemical products, and freshwater; however, the role of mangroves in climatic and hydrologic modulation, erosion control, protection against natural hazards, soil formation, and nutrient cycling has been recently recognized. In addition, different mangrove types (e.g., riverine, fringing, basin) provide specific services and support coastal fisheries to a different extent [6,7], but they may also provide differential carbon capture capabilities [8][9][10][11].…”

An attempt to recover economic losses from decadal changes in two lagoon systems of Sri Lanka through a newly patented mangrove product

“…Although mangrove ecosystems provide outstanding economic uses and invaluable ecological services, they are still decreasing in surface around the world (Kathiresan & Bingham, 2001) and ranked among the most threatened of coastal habitats, particularly those in developing countries in tropical regions (Saenger et al, 1983). Also in Sri Lanka, mangroves are one of the most misused and threatened coastal eco-systems, and recurrently scientists emphasise the need for mangrove conservation (Dahdouh-Guebas et al, 2002, 2005c and for early detection of its degradation (Dahdouh-Guebas et al, 2005a;Dahdouh-Guebas et al, 2005b). This situation is aggravated by the fact that a considerable portion of the country's mangrove lands are privately owned properties (IUCN, 1996(IUCN, , 2000.…”

Intense Habitat-Specific Fisheries-Induced Selection at the Molecular Pan I: Locus Predicts Imminent Collapse of a Major Cod Fishery

“…Second, the respondents' distinctions between true mangrove species and mangrove associates may also have biased our a posteriori confrontation with remote sensing data. They reported for instance the dramatic expansion of the mangrove associate Acanthus ilicifolius, but this type of distinction of herbaceous plants is possible only with imagery with submeter spatial resolution, such as IKONOS [66]. In addition, expansion of socalled mangrove species, which in reality are mangrove associated species, may lead to misinterpretation and may mask cryptic ecological degradation in mangrove ecosystems and jeopardise functionality [16,64].…”