User:JamaicaPaleoProject/sandbox

Article Evaluation
I chose the page, "Geography of Jamaica" (Geography of Jamaica), for my article evaluation. I chose to evaluate this article because a good understanding of physical geography is fundamental to ecology, and specifically to the subfields of paleoecology and biogeography. Furthermore, my graduate field research site is located in southwestern Jamaica, and I was interested in perusing Wikipedia articles that were pertinent to my academic studies.

I believe that the content of the article, which discussed the physical landforms and landscape of Jamaica, climate, and biota, was relevant to the topic of the article. I did not find any aspects of the article to be distracting. The article was written from a neutral perspective, and the content was unbiased in its representation of the island's geography. I found that the sections that focused on the geology and climate of Jamaica were far more developed relative to the section about vegetation and wildlife. Consequently, I believe that there was an over-representation of information related to physical aspects of Jamaican geography, with a more minimal focus on relationships between the island's geography and ecology.

All the citation web links included in the article work, and the cited sources support the claims made in the article. However, each fact stated in the article is not referenced with an appropriate citation, and I find that one of the few cited sources, FiWi Roots.com--a non-profit organization committed to celebrating and commemorating Jamaican culture and natural history--may qualify as a biased source. Information from that site may not have undergone an adequate peer review process, and might be intentionally stated in a fashion that highlights only certain facts about Jamaica. On the other hand, the other sources referenced--a published journal article and the book "Encyclopedia of Earth", which was commissioned by the National Council for Science and the Environment, appear to be neutral, reputable, and unbiased sources. The content of the article is up-to-date, however, I believe that the article could be improved by further developing the section titled "Vegetation and wildlife". Increased attention could be paid to discussing the modern plant and animal communities inhabiting the island, with special references to endemism, endangered species and areas of high conservation importance. Furthermore, the article would benefit from placing Jamaican ecological communities in the broader context of global species diversity, and also within the framework of current global and local biodiversity stressors.

Several conversations were initiated on the article's talk page, mostly centered on the clarification of facts included in the article, proposing images that could be placed in the article (e.g. a physical map of Jamaica), and outlining revisions or suggestions that could enhance the overall quality of the article. The article is a part of WikiProject Caribbean and WikiProject Geology, and is rated as "High-importance" and "Low-importance" respectively, on each of the WikiProject's importance scales. Some comments and suggestions mentioned on the article's Talk page were presented without specifically identifying the sections that needed revision--that is, comments were vague--or, supporting facts were offered without any associated citations/references. In class and during the online training, an important point that was raised was to be courteous and thorough while making suggestions on the Wikipedia Talk page, and to add fact-based, reputable information from reliable sources to article discussions. Furthermore, the original sources containing the facts to be added should be referenced at all points throughout the Wikipedia editing process.

Optional assignment: Completed on article's Talk page.

Assigned Article-Megafauna
I plan to update the subsection of the article titled Megafauna called "Consequences of depletion of megafauna". This subsection currently discusses the effects of megafaunal populations on nutrient transport and methane emissions; however, the article lacks substantive information about megafaunal impacts on vegetation communities. I believe that the article would benefit from the inclusion of information about the effects of megafaunal extinction on the composition, structure and diversity of plant communities, in addition to a broader discussion about how these ecological changes may influence physical environmental factors such as landscape openness, light availability, and fire regimes. My current plan for updating the article focuses on three primary mechanisms by which megafaunal activity or collapse can alter vegetation dynamics: 1) selective grazing/browsing, 2) seed dispersal of megafauna-adapted plants, and 3) physical modification of the environment via trampling, uprooting of large trees etc. Furthermore, I plan to discuss the relationship between megafauna and these ecological processes using information from both modern observations and field experiments, and the paleoecological record. It is my hope that outlining the impacts of megafauna on vegetation communities and landscapes will further illuminate the ecological implications of past and present megafaunal declines, and ultimately, improve the overall quality of the chosen Wikipedia article.

In order to comprehensively address my discussion points, I will rely on information from the sources listed below:

Effects of Megafauna on Vegetation
Megafauna, as a result of their large body size and unique life history traits (e.g. high trophic requirements, large home ranges), can cause significant alteration to vegetation communities. These ecological changes may precipitate as shifts in the composition and/or structure of the vegetation of a region, or as distributional shifts in the ranges of different plant species. Furthermore, the resulting changes in vegetation dynamics can modify the abiotic environment in myriad ways, including changes in understory light availability, landscape openness, and the frequency and intensity of fire events. Consequently, many megafaunal species have been classified as "keystone species" or "ecosystem engineers", due to their strong and wide-ranging impacts on ecological function and processes, and the disproportionately large effects that these changes have on the biodiversity of ecological communities. Megafaunal activity, or the lack thereof, can alter vegetation dynamics via selective browsing and/or grazing on different plant taxa, acting as seed dispersers, and physical modification of the structural environment. Evidence for the role of megafauna in shaping vegetation communities via the above-mentioned mechanisms arises from both the paleoecological record, and from contemporary field experiments and observations. These studies highlight the important ecological ramifications of megafaunal loss in both past and present temporal contexts, and draw attention to the ongoing decline of megafauna being experienced at the global scale.

Megafaunal decline can have significant impacts on the composition and structure of vegetation communities, as a result of the release from herbivory of plant taxa that megafaunal species preferentially feed upon. That is, high megafaunal abundances limit the proliferation of certain plant species due to selective feeding behaviors, and a decrease in megafaunal populations causes a relaxation of herbivory pressure, and consequent increases in plants that were heavily browsed/grazed upon. For example, a multi-proxy paleoecological record from the upper Midwestern United States indicated that the collapse of local megafaunal populations at approximately 13,700 years ago was associated with the proliferation of the hardwood tree species, black ash (Fraxinus nigra), hophornbeam (Ostrya) and ironwood (Carpinus), coeval with a period of high spruce (Picea) abundances. The composition of plant species in the resultant vegetation community, that is, abundant hardwood trees and spruce, has no present-day analog. Similarly, the analysis of pollen, charcoal, and Sporormiella abundances in swamp sediments collected from northeastern Australia, suggested that megafaunal declines at approximately 41,000 years ago were linked to a shift from rainforest-type vegetation to dominance by grasses and sclerophyllous taxa. In both of the above-mentioned studies, increased fire regimes followed the decline of megafauna, and the researchers hypothesized that the observed enhancement of fire intensity was at least partly due to the accumulation of fuel that would have been otherwise consumed by the once-abundant megafauna. A contemporary exclusion experiment conducted in the semi-arid savanna of Kenya demonstrated that selective feeding of large herbivores resulted in a shift in plant community dominance from palatable, broad-leaved species, such as Grewia tenax, to unpalatable, thorny shrubs, such as Acacia . Indeed, modern experimental evidence suggests that increased thorn length and density are inducible plant defensive responses that serve to reduce herbivory, thus highlighting the important role of plant-herbivore interactions in determining savannah vegetation structure and composition. Close to a decade of monitoring at the Ithala Game Reserve, South Africa revealed that heavy feeding activity by elephants, black rhinoceros and other browsers was associated with significant shifts in plant community composition, including sharp declines in Aloe marlothii, Acacia nilotica, Acacia davyi and other woodland species, and increased abundances of unpalatable species, such as Euclea racemosa and Euclea crispa. Researchers documented significant reductions in Acacia spp. abundances after giraffe introduction to a southern African savannah, while noting that areas with steep terrain that provided spatial refugia from giraffe browsing did not experience similar elevated levels of tree mortality.

Large herbivore removal from vegetated areas can also have significant influences on the frequency and intensity of disturbance events via controlling the landscape availability of flammable biomass. For example, megaherbivore exclosures in a wooded African savannah were associated with increased tree densities and fine fuel accumulation, which resulted in more intense fires. Selective moose (Alces alces) browsing can shift forest community composition from deciduous trees (e.g. Populus tremuloides, Betula, Corylus) to spruce (Picea) dominance, which reduces nutrient availability and net primary productivity due to decreased quality of leaf litter inputs to the soil. Results from paleoecological studies as well as modern experiments indicate that shifts in vegetation community composition and structure may result from megafaunal decline, and thus constitutes an important ecological consequence of megafaunal loss from ecosystems. These ecological changes may modify abiotic processes, such as fire regimes and biogeochemical cycling, and can have differential cascading effects on the diversity of other fauna that co-inhabit the affected ecosystems, including ants, spiders , and rodents. Megafaunal decline could result in the disruption of seed dispersal relationships between plants with megafauna-adapted dispersal traits and imperiled large herbivores. Plant species that are vulnerable to the loss of seed dispersal services provided by megafauna exhibit a suite of seed and fruit traits that is collectively referred to as "megafaunal dispersal syndrome". These traits include: large fruits, large seeds that are often covered by a thick seed coat or smaller seeds that are encased in a hard nut, fruits that fall off the tree prior to or at maturation, fruits that do not typically attract arboreal and volant dispersers, fruits that are consumed freely by modern domesticated animals like horses and cattle or extant megafauna such as elephants and tapirs, and trees that are usually not found in areas that are inaccessible to potential megafauna dispersers, such as steep slopes. Given that global megafauna populations plummeted after the end-Pleistocene extinction event, the observation of these megafauna-adapted seed and fruit traits in numerous plant species suggest that many extant plants may already experience dispersal limitation problems as a result of the loss of their co-evolved dispersal agents, or a lack of suitable surrogate dispersers that may wholly or partially compensate for past megafaunal declines. However, the characteristic traits that define megafauna dispersal syndrome would have been ecologically advantageous in the context of prehistoric megafauna-rich ecosystems. Extant plant species that have seed and fruit traits consistent with megafaunal dispersal syndrome include, but are not limited to: Crescentia alata, Prosopis juliflora, Balanites wilsoniana, and Spondias spp. .

Contemporary research has illuminated the key role of extant megafauna in seed dispersal processes, and thus, in maintaining landscape-level tree diversity. A literature analysis showed that elephants either consume the fruit or disperse the seed of approximately 450 plant species from about 268 genera across their range, giving them the name "megagardeners of the forest". Furthermore, a study in the Democratic Republic of Congo found that fourteen forest tree species were dependent on elephants for seed dispersal, and these tree species experienced poor recruitment due to poaching-induced elephant decline and consequent increases in density-dependent seedling mortality. Endemic Galapagos tortoises (Chelonoidis nigra) were found to be effective long distance seed dispersers of both native and introduced plants, dispersing the seeds of approximately 45 plant species up to several thousand meters away from the parent plant. Similarly, Greater one-horned rhinoceroses (Rhinoceros unicornis) were shown to be important dispersers of the megafauna-adapted plant Trewia nudiflora in southern Nepal, as they transport and deposit large numbers of its seeds, and promote seedling growth via the provision of nutrients in manure. Further megafaunal decline has the potential to disrupt coevolutionary interactions between plants and their large-bodied seed dispersal agents, which may lead to future compositional shifts in vegetation, range reductions and poor recruitment in megafauna-adapted plant species, and at the extreme, local extirpation and species extinction, particularly in the absence of compensatory dispersal strategies. The widespread impacts of megafaunal activity, including uprooting of trees, bark removal, and branch breaking, on the physical structure of vegetation are well-documented, particularly in regions such as Africa, where extant megafauna occur at high densities. Male elephants can topple over four trees per day annually, and up to nine trees per day during the dry season. A study in northeastern South Africa demonstrated that mean treefall rates were five times higher in areas that contained elephants compared to an adjacent nature reserve that lacked elephants. Similarly, high elephant densities in the Zambezi Valley escarpment of Zimbabwe were associated with reductions in tree cover and density, and increased shrub encroachment, which resulted in a decline in the diversity of ants and woodland birds in elephant-impacted habitats. Vegetation modification by elephants can increase landscape openness and light penetration through the canopy, which facilitates gap colonization by herbs and grasses, and promotes formation of woodland-grassland mosaic habitats. These vegetation shifts can result in an increase in grazers and decrease in browsers where elephant activity has facilitated the spread of grasses. Elephant damage to woody trees has also been shown to have a positive effect on herpetofaunal species richness due to the creation of new habitats that can be utilized for hunting, breeding, and/or for refugia from predators. Similar positive effects were reported for local population densities of the gecko Lygodactylus keniensis in areas with high densities of elephant-damaged trees, due to the creation of refugia for the lizards via bark stripping and branch breaking. Paleoecological and paleontological evidence also point to the transformative ecological role of extinct megafauna in prehistoric ecosystems. Indeed, researchers hypothesize that megafauna trampling caused a shift in dominance from mosses to fast-growing grasses in tundra ecosystems, and was a critical ecological process for maintaining the iconic Pleistocene mammoth-steppe biome. Previous research highlights the key role of megafauna as ecosystem engineers that can alter the three-dimensional structure of plant communities by using brute force to physically modify woody vegetation. These megafauna-induced changes in the structural characteristics of vegetation communities can have significant impacts on both plant and animal diversity and ecological interactions, and would be greatly minimized in the event of megafaunal population decline.

Megafauna diversity has a critical role in influencing the vegetation dynamics of ecosystems, whereby past fluctuations in megafaunal populations have been implicated as the primary driving force behind large-scale reorganizations of regional plant communities, and biome-scale changes in vegetation patterns. Contemporary studies also highlight how the reintroduction of megafaunal species to areas where they were historically absent can restore key ecological functions and processes related to vegetation, and thus, from a biodiversity and conservation management standpoint, induce ecosystems to shift towards a more desirable state. Consequently, severe declines in megafaunal population numbers, local extirpation, or extinction represent a loss of these important ecological services, and can confer major changes to the stability and resilience of vegetation communities. Extant megafauna are experiencing severe population declines at the global scale due to a variety of factors, including poaching, habitat fragmentation, climate change, and human and livestock encroachment. The ecological impacts of this most recent wave of declines in megafaunal populations on vegetation community composition, structure and function pose several unresolved questions and remains a field of active research.