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Abstract
Vegetation canopies represent the main ecosystems on intertidal landforms and they clearly respond to changes in coastal environments. Climate change, including temperature, precipitation and sea level rise, are affecting the health and distribution of coastal vegetation, as well as the runoff and sedimentation rates that can impact coastal areas. This study has used the normalized difference vegetation index (NDVI) to investigate vegetation canopy dynamics on three different coastal sites in southeastern Australia over the past 47 years (1975–2015). NDVIs temporal-datasets have been built from satellite images derived from Landsat 1–8. These were then regressed to the climatic and geomorphic variables. Results show clear increases in NDVI at Towamba and Wandandian Estuaries, but a decline at Comerong Island (southeastern Australia). The sedimentation rate has the most significant positive impact on NDVI since it has the potential to provide additional space for vegetation. Temperature and sea level rise have positive effects, except on Comerong Island, but rainfall has no significant effect on the NDVI at any site. Different NDVI trends have been recorded at these three coastal sites reflecting different correlations between the vegetation, climatic and geomorphic (as independent) variables. The geomorphological characteristics of the highly-dynamic intertidal estuarine landforms, which are subject to active erosion and deposition processes, have the largest impact on vegetation cover and, hence, on NDVI. Assessing the vegetation canopy using NDVI as an evaluation tool has provided temporal-dynamic datasets that can be correlated to the main individual environmental controls. Such knowledge will allow resource managers to make more informed decisions for sustainable conservation plans following the evaluation the potential consequences of any environmental changes.
Highlights
Visualizing and analysing the vegetation dynamics of the three study sites has been accomplished using normalized difference vegetation index (NDVI) derived from Landsat data over the last 40 years (1975 2015; Figures 7 13)
This paper has focused more on the ecological side, as presented by the vegetation dynamics, so only the positive values have been interpolated statistically (0 to 1) to represent greenness canopies (Figures 7b, 10b and 12b)
A clear variation of vegetation reaction has occurred at these three coastal sites, resulting in different NDVI trends and different correlations with the climatic and sea level factors
Summary
Regional and local landscape scales, vegetation responses are affected by whichever climatic factors represent the dominant limitation to plant growth [6]. In a coastal-dynamic context, changes in vegetation conditions can be categorised as those affected by temperature and precipitation that impact growth and productivity, as well as those that affect the landform stabilities, including sea level and sedimentation dynamics [7 11]. Coastal wetlands are the most sensitive and responsive coastal ecosystems to environmental pressures, such as climate change, the rising sea level and the current stage of human settlements, which control most of the coastal processes [8,14 16]. Coastal ecosystems may be affected by a local surge in surface temperature, precipitation decline, and sea level rise (SLR) under current climate scenarios. Human activities have been shown to have a substantial effect on coastal ecosystems (e.g., via habitat destruction and biodiversity reduction) [17], which implies that there is a great need to detect and predict changes in ecosystem functioning
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