Climate change and other anthropogenic factors have caused a significant decline in seagrass cover globally. Identifying the specific causes of this decline is paramount if they are to be addressed. ...Consequently, we identified the causes of long-term change in seagrass/submerged aquatic vegetation (SAV) percentage cover and extent in a marine protected area on Jamaica’s southern coast. Two random forest regression (RFr) models were built using 2013 hydroacoustic survey SAV percentage cover data (dependent variable), and auxiliary and 2013 Landsat 7 and 8 reflectance data as the predictors. These were used to generate 24 SAV percentage cover and benthic feature maps (SAV present, absent, and coral reef) for the period 1984–2021 (37 years) from Landsat satellite series reflectance data. These maps and rainfall data were used to determine if SAV extent/area (km2) and average percentage cover and annual rainfall changed significantly over time and to evaluate the influence of rainfall. Additionally, rainfall impact on the overall spatial patterns of SAV loss, gain, and percentage cover change was assessed. Finally, the most important spatial pattern predictors of SAV loss, gain, and percentage cover change during 23 successive 1-to-4-year periods were identified. Predictors included rainfall proxies (distance and direction from river mouth), benthic topography, depth, and hurricane exposure (a measure of hurricane disturbance). SAV area/extent was largely stable, with >70% mean percentage cover for multiple years. However, Hurricane Ivan (in 2004) caused a significant decline in SAV area/extent (by 1.62 km2, or 13%) during 2002–2006, and a second hurricane (Dean) in 2007 delayed recovery until 2015. Additionally, rainfall declined significantly by >1000 mm since 1901, and mean monthly rainfall positively influenced SAV percentage cover change and had a positive overall effect on the spatial pattern of SAV cover percentage change (across the entire bay) and gain (close to the mouth of a river). The most important spatial pattern predictors were the two rainfall proxies (areas closer to the river mouth were more likely to experience SAV loss and gain) and depth, with shallow areas generally having a higher probability of SAV loss and gain. Three hurricanes had significant but different impacts depending on their distance from the southern coastline. Specifically, a hurricane that made landfall in 1988 (Gilbert), resulted in higher SAV percentage cover loss in 1987–1988. Benthic locations with a northwestern/northern facing aspect (the predominant direction of Ivan’s leading edge wind bands) experienced higher SAV losses during 2002–2006. Additionally, exposure to Ivan explained percentage cover loss during 2006–2008 and average exposure to (the cumulative impact of) Ivan and Dean (both with tracks close to the southern coastline) explained SAV loss during 2013–2015. Therefore, despite historic lows in annual rainfall, overall, higher rainfall was beneficial, multiple hurricanes impacted the site, and despite two hurricanes in three years, SAV recovered within a decade. Hurricanes and a further reduction in rainfall may pose a serious threat to SAV persistence in the future.
•Road density doubled in 68 years and resulted in simplification of forest patch shapes.•Initial deforestation and fragmentation influenced by road forest reserves.•Total and core forest increased ...and forest loss reduced after reserve designation.•Increased deforestation and fragmentation in the 1980s and the 2000s.•This is due to complex pattern of human encroachment, not influenced by roads or the reserves.
Historical data on landuse changes are important for interpreting the current status of natural systems such as forests. Analyses of road network dynamics can be particularly useful as network expansion is often a precursor to and an indicator of increased human activity. Legal protection is often seen as the most viable option available for protecting natural forests; but over the past decade, its effectiveness has been questioned. We assessed the impact of roads and the designation of a forest reserve on deforestation and forest fragmentation in a tropical moist forest, Cockpit Country, Jamaica, from 1942 to 2010. Specifically, we classified multi-temporal images (black and white aerial photographs, IKONOS and GeoEye images) using an object based image analysis and we included a vector of digitized roads for each year of assessment during the classification process. We then conducted a fragmentation analysis of the classified images and assessed the relationship between road density and several fragmentation metrics over time, and the spatial influence of the reserves (presence/absence) and roads (Euclidean distance from roads) on deforestation and several fragmentation metrics using generalized linear models.
Between 1942 and 2010, road density nearly doubled (from 0.67km/km2 to 1.22km/km2), with significant increases occurring within forest reserves, and was significantly related to the area-weighted mean shape index of the forest (forest patches became more regularly shaped and linear). Initially, relatively high deforestation rates and high levels of fragmentation between 1942 and 1961 were likely related to the large increase in road density. Deforestation and forest fragmentation were more likely to occur closer to roads over all time periods, and the magnitude/significance of this relationship peaked in subsequent time periods after road density doubled; but in the final time period, its influence declined. Legal protection afforded to the forest in the 1950s and 1960s coincided with an increase in total and core forest area and a reduction in deforestation rate, and deforestation and forest fragmentation were significantly lower inside the reserve. Therefore, the Forest Reserves were initially effective; however, their effectiveness waned after 1980. Increased deforestation and fragmentation in the 1980s and the 2000s indicate a more complex pattern of human encroachment, as these changes do not appear to have been influenced by changes to the road network, or by the presence of the Forest Reserves. Further research into the factors influencing human use of these forested areas is needed for effective management of the area.
We investigated the use of full-range (400–2,500 nm) hyperspectral data obtained by sampling foliar reflectances to discriminate 46 plant species in a tropical wetland in Jamaica. A total of 47 ...spectral variables, including derivative spectra, spectral vegetation indices, spectral position variables, normalized spectra and spectral absorption features, were used for classifying the 46 species. The Mann–Whitney U-test, paired one-way ANOVA, principal component analysis (PCA), random forest (RF) and a wrapper approach with a support vector machine were used as feature selection methods. Linear discriminant analysis (LDA), an artificial neural network (ANN) and a generalized linear model fitted with elastic net penalties (GLMnet) were then used for species separation. For comparison, the RF classifier (denoted as RFa) was also used to separate the species by using all reflectance spectra and spectral indices, respectively, without applying any feature selection. The RFa classifier was able to achieve 91.8% and 84.8% accuracy with importance-ranked spectral indices and reflectance spectra, respectively. The GLMnet classifier produced the lowest overall accuracies for feature-selected reflectance spectra data (52–77%) when compared with the LDA and ANN methods. However, when feature-selected spectral indices were used, the GLMnet produced overall accuracies ranging from 79 to 88%, which were the highest among the three classifiers that used feature-selected data. A total of 12 species recorded a 100% producer accuracy, but with spectral indices, and an additional 8 species had perfect producer accuracies, regardless of the input features. The results of this study suggest that the GLMnet classifier can be used, particularly on feature-selected spectral indices, to discern vegetation in wetlands. However, it might be more efficient to use RFa without feature-selected variables, especially for spectral indices.
•We modelled long-term socio-economic and spatial pattern drivers of landuse change.•Considerable temporal variation among the most important drivers for each period.•Recently, factors related to ...access no longer a deterrent to deforestation.•Thus, deforestation increased in reserves and largest, contiguous forest blocks.
Very little research has considered the underlying drivers of land cover change in Caribbean islands, particularly in those islands that are still experiencing a net loss of forest cover. We investigated the underlying driving forces (socio-economic drivers) and spatial pattern drivers (biophysical features) of both deforestation and reforestation in the Cockpit Country, Jamaica. This area is one of the most globally important sites for plant diversity, but is threatened by clearance for small-scale agriculture. Drivers of change were assessed for both the individual time steps within the study period (1942–2010) and for the entire 68 years using multivariate, spatially explicit, statistical models. The primary drivers of deforestation over the study period were accessibility (gentler slopes, closer to forest edges, more fragmented forests) and greater relative wealth/socio-economic status (increased access to piped water). Reforestation generally increased closer to forest edges and in areas with lower market access (greater distances to roads and towns) and lower wealth/status (increased reliance on pit latrines). We found considerable temporal variation among the most important drivers for each time step, including climate, employment status, population density, population age structure and relative wealth. Forest reserve status was not a key determinant of deforestation but did increase the probability of reforestation between 1961 and 1980. During the final time step (2001–2010) access was less important as a deterrent to deforestation, which increased within the most contiguous forest blocks. If the deforestation drivers of the last decade do not change, deforestation is predicted to occur within the forest reserves, and in the largest, least fragmented forest blocks. Thus, conservation and management strategies for our study site must seek to address issues related to both enforcement and the socio-economic factors that influence deforestation and habitat fragmentation.
Hydroacoustic and optical remote sensing have been commonly used to map shallow nearshore benthic features. However, the number, type, scale, and accuracy of the mapping products that can be obtained ...from the two sensors differ; as such, there can be limited agreement between their mapping products. These differences can be further accentuated if the hydroacoustic data are interpolated to produce a map. Interpolation introduces spatial uncertainty and reduces map accuracy. Consequently, maps generated from the two sensors may provide dissimilar spatial and temporal representations of the same benthic features. We therefore compared the performance of a random forest regression (RFr) and a universal kriging (UK) interpolation method and a post-classification enhancement that can be used to increase the accuracy and complementarity of benthic habitat maps derived from hydroacoustic data. First, we used single beam echosounder (SBES) survey bathymetry data from the Bluefields Bay marine protected area (MPA) in western Jamaica (13.82 km
2
in size), to create a bathymetric surface model (BSM), from which rugosity and bathymetric position index (BPI) maps were generated. Next, the RFr was used to create submerged aquatic vegetation (SAV) percentage cover maps from the SBES SAV cover data by predicting cover at un-sampled locations. Predictors included auxiliary data such as depth, BPI, survey points coordinates and radiometrically corrected, deglinted and water column corrected image reflectance index values from each of the following: WorldView-2, Geoeye-1 and Landsat 8. Additionally, a SAV map was created using the UK. The most accurate SAV cover thresholds were identified and were used to create binary maps from the RFr and UK maps. A rugosity derived coral reef map was then added to the binary maps. The resulting benthic habitat maps had comparable accuracies and class coverage to benthic maps classified from GeoEye-1 and WorldView-2 images using pixel and object-based classifiers. However, map accuracies were calculated using a suboptimal number of reference points (<50) for two of the benthic map classes (SAV absent and coral reef). This was not considered to be problematic as the addition of the coral reef class to the binary maps resulted in a significant decrease in uncertainty (standard error and confidence interval width of the overall accuracy) and a significant increase in the user's accuracy of the SAV absent map class. Also, the difference in uncertainty and accuracy between the map classes did not change. The methods used in this study can therefore be used to increase the accuracy (and to decrease the uncertainty) and the complementarity of maps derived from hydroacoustic data.
The last remaining Amazonian-type swamp forest fragments in Black River Lower Morass, Jamaica, have been subjected to a myriad of anthropogenic disturbances, compounded by the establishment and ...spread of several invasive plant species. We established 44 permanent sample plots (covering 3.92 ha) across 10 of these swamp forest fragments and sampled all non-woody plants and all trees ≥2 cm DBH found in the plots. These data were used to (1) identify thresholds of hybridity and novelty, (2) derive several diversity and structural descriptors used to characterize the swamp forest fragments and (3) identify possible indicators of anthropogenic degradation. These were incorporated into a framework and used to determine the status of the swamp forest fragments so that appropriate management and conservation measures can be implemented. We recorded 43 woody plant species (9 endemic, 28 native and 4 non-native) and 21 non-tree species. The composition and structure of all the patches differed significantly due to the impact of the herbaceous invasive plant
Alpinia allughas
, the presence and diversity of other non-native plants, and differing intensities of anthropogenic disturbance (e.g., burning, cutting and harvesting of non-timber forest products). We ranked forest patches along a continuum representing deviations from a historical proxy (least disturbed) swamp forest to those with dramatically altered structural and floristic attributes (=novel swamp forests). Only one fragment overrun with
A. allughas
was classified as novel. If effective conservation and management does not come to the BRLM, the remaining swamp forest fragments appear doomed to further degradation and will soon disappear altogether.
Jamaica experienced net deforestation during the period 2001–2010. Yet, the proximate causes of deforestation and the reasons why a forest transition might be absent, particularly at the local-level, ...which can explain national scale changes, have been little studied. Long-term changes in socio-economic and land cover data over 68-years, for the moist forest of the Cockpit Country, Jamaica, and predictors of land cover change, were assessed using generalized linear and non-linear regression models. These were used to determine if the classic theorized determinants of a forest transition were present at different spatial scales and to identify the proximate cause(s) of deforestation. Some theorized determinants were present (improvements in national and sub-national economic development, and a decline in agricultural production); however, rural/local scale population density and growth rates were stable. As such, pressure on the unprotected (non-reserves) marginal/agricultural lands in the Cockpit Country was not reduced and this prevented them from reverting to forest. Forest cover for the entire Cockpit Country and the non-reserves therefore fluctuated significantly over time (nonlinear trend), peaking twice (1980 and 2002). The implementation of trade liberalization policies in the 1980s resulted in increased yam cultivation, which was the proximate cause of forest cover change in the non-reserves (a significant non-linear relationship). As a result, deforestation increased significantly during this period and again during the 2000s, at which time it was driven largely by other factors. A forest transition is unlikely to occur via an economic pathway, but it can possibly be achieved via the enforcement of existing forest protection laws and active promotion of forest cover expansion.
► We take a longitudinal approach to study the dynamics of tropical dry forests. ► Gap dynamics cannot be used to describe regeneration in this dry forest ecosystem. ► Despite a shift in species ...dominance, secondary succession did not occur. ► Coppice canopy establishment ameliorates the harsh understorey conditions.
Changes in forest structure, the rate of recovery and stem turnover, 10
years after experimental cutting of a primary tropical dry forest in Jamaica, were determined by conducting a post-disturbance inventory of permanent sample plots in 2009. In April 1999, two plots within each of four blocks were assigned to two randomly allocated treatments (partially and clear cut) and a plot was assigned as a control (uncut). The treatment intensities were intended to mimic wood extraction for charcoal or timber production, a common form of anthropogenic disturbance in Caribbean dry forests. The application of the treatments significantly reduced the number of trees per diameter size-class, but after 10
years, the size-class distribution for the small size-classes was similar to pre-disturbance measurements. However, larger size-classes (⩾14
cm) in 2009 had fewer individuals when compared with the pre-disturbance size-class distribution. Ten years after cutting, tree height, basal area and tree density in partially cut plots had recovered by 92%, 81% and 94% and in clear cut plots by 78%, 35% and 78% respectively, in comparison with control plots. Although the biomass lost due to cutting and the original state of this forest have not fully recovered 10
years after disturbance, our results showed that coppicing allows the establishment of some semblance of a canopy and offers a rapid route to reclaim space. This newly established canopy also helps to ameliorate environmental conditions facilitating regeneration by seed, which would otherwise take years to occur due to the harsh conditions found in open areas. No new species or any species that could be described as pioneers were recorded and despite a shift in dominance, secondary succession did not occur. Therefore gap dynamics, often used to describe the process of regeneration in tropical rainforests, cannot be used to describe regeneration in this dry forest ecosystem.
Changes in forest structure, the rate of recovery and stem turnover, 10years after experimental cutting of a primary tropical dry forest in Jamaica, were determined by conducting a post-disturbance ...inventory of permanent sample plots in 2009. In April 1999, two plots within each of four blocks were assigned to two randomly allocated treatments (partially and clear cut) and a plot was assigned as a control (uncut). The treatment intensities were intended to mimic wood extraction for charcoal or timber production, a common form of anthropogenic disturbance in Caribbean dry forests. The application of the treatments significantly reduced the number of trees per diameter size-class, but after 10years, the size-class distribution for the small size-classes was similar to pre-disturbance measurements. However, larger size-classes (⩾14cm) in 2009 had fewer individuals when compared with the pre-disturbance size-class distribution. Ten years after cutting, tree height, basal area and tree density in partially cut plots had recovered by 92%, 81% and 94% and in clear cut plots by 78%, 35% and 78% respectively, in comparison with control plots. Although the biomass lost due to cutting and the original state of this forest have not fully recovered 10years after disturbance, our results showed that coppicing allows the establishment of some semblance of a canopy and offers a rapid route to reclaim space. This newly established canopy also helps to ameliorate environmental conditions facilitating regeneration by seed, which would otherwise take years to occur due to the harsh conditions found in open areas. No new species or any species that could be described as pioneers were recorded and despite a shift in dominance, secondary succession did not occur. Therefore gap dynamics, often used to describe the process of regeneration in tropical rainforests, cannot be used to describe regeneration in this dry forest ecosystem.
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