Historical Degradation and Ecological Recovery

2019 ◽  
pp. 31-58
Author(s):  
Todd J. Braje ◽  
Jon M. Erlandson ◽  
Kristina M. Gill ◽  
Torben C. Rick ◽  
Linda Bentz ◽  
...  
Keyword(s):  
Soil Erosion ◽  
Baja California ◽  
Exotic Plants ◽  
Ecological Impacts ◽  
Commercial Fisheries ◽  
Human Occupation ◽  
Island Ecosystems ◽  
Ecological Changes ◽  
Ecological Baselines ◽  
Ecological Recovery

Spanish arrival to Alta and Baja California in AD 1542 marked the beginning of widespread ecological changes for California Island ecosystems. Over several centuries, Native peoples were removed to mainland towns and missions, intensive commercial fisheries and ranching operations developed, and numerous exotic plants and animals were introduced. The ecological fallout was swift and extensive, with extinctions and extirpations, devegetation, severe soil erosion, damaged hydrology, collapsed fisheries, and other ecological impacts. Archaeologists have long recognized some of the effects of these historical impacts, but only after decades of restoration biology on the islands have we come to appreciate how dramatically ecological baselines have shifted since Spanish arrival. As a result, many of California's islands now appear to have been optimal rather than marginal for human occupation.

scholarly journals Variable impact of late-Quaternary megafaunal extinction in causing ecological state shifts in North and South America

2015 ◽  
Vol 113 (4) ◽  
pp. 856-861 ◽  
Author(s):  
Anthony D. Barnosky ◽  
Emily L. Lindsey ◽  
Natalia A. Villavicencio ◽  
Enrique Bostelmann ◽  
Elizabeth A. Hadly ◽  
...  
Keyword(s):  
United States ◽  
Late Quaternary ◽  
Critical Role ◽  
Ecological Impacts ◽  
Individual Species ◽  
Ecological State ◽  
Ecological Changes ◽  
Two Factors ◽  
Large Animals ◽  
Short Time

Loss of megafauna, an aspect of defaunation, can precipitate many ecological changes over short time scales. We examine whether megafauna loss can also explain features of lasting ecological state shifts that occurred as the Pleistocene gave way to the Holocene. We compare ecological impacts of late-Quaternary megafauna extinction in five American regions: southwestern Patagonia, the Pampas, northeastern United States, northwestern United States, and Beringia. We find that major ecological state shifts were consistent with expectations of defaunation in North American sites but not in South American ones. The differential responses highlight two factors necessary for defaunation to trigger lasting ecological state shifts discernable in the fossil record: (i) lost megafauna need to have been effective ecosystem engineers, like proboscideans; and (ii) historical contingencies must have provided the ecosystem with plant species likely to respond to megafaunal loss. These findings help in identifying modern ecosystems that are most at risk for disappearing should current pressures on the ecosystems’ large animals continue and highlight the critical role of both individual species ecologies and ecosystem context in predicting the lasting impacts of defaunation currently underway.

THE GULF WAR OIL SPILL TWELVE YEARS LATER: CONSEQUENCES OF ECO-TERRORISM

2005 ◽  
Vol 2005 (1) ◽  
pp. 957-961 ◽  
Author(s):  
Jacqueline Michel ◽  
Miles O. Hayes ◽  
Charles D. Getter ◽  
Linos Cotsapas
Keyword(s):  
Oil Spill ◽  
Salt Marshes ◽  
Large Scale ◽  
Gulf War ◽  
Tidal Flats ◽  
Ecological Impacts ◽  
Chemical Toxicity ◽  
Habitat Recovery ◽  
Intertidal Habitats ◽  
Ecological Recovery

ABSTRACT The intentional release of an estimated 11 million barrels of oil during the 1991 Gulf War was the largest oil spill in history. An assessment of the physical, chemical, and ecological impacts of this spill shows that, 12 years later, oil residues and habitat modifications continue to have toxic effects on intertidal communities. As of 2003, there are an estimated 8 million cubic meters of oiled sediment remaining along the 803 km of impacted shoreline in Saudi Arabia. Of this volume, 45% occurs in muddy tidal flats and 23% in salt marshes and mangroves. Much of the oil in these sheltered habitats occurs as oiled crab burrows, with liquid oil remaining in the burrows to depths that exceed 50 cm. These habitats show the lowest degree of ecological recovery since the spill, with 87% of the upper intertidal zones of mangroves and marshes and 71 % of muddy tidal flats having reduced species richness and a disturbed community structure. Those habitats exposed to the greatest amount of wave activity contain the smallest amount of residual oil; however, on outer sand beaches, the oil is commonly buried to depths exceeding 1 m. The factors that affect the ecological recovery of the intertidal habitats include: 1) The chemical toxicity of the oil residues; 2) the physical toxicity of heavy and hardened oil residues; 3) other physical barriers that affect seed germination of plants, settlement of larvae, and burrowing; 4) limited sources for recruitment of biota; 5) reduced hydrological functioning of tidal channels. This study shows the importance of oil removal as the first phase of habitat recovery. It also indicates the potential for large-scale damage by blatant acts of eco-terrorism.

Analysis of forest types and estimates of biomass in the Sierra de La Laguna Reserve, Baja California Sur, Mexico

2010 ◽  
Vol 40 (10) ◽  
pp. 2059-2068 ◽  
Author(s):  
José Luis León-de la Luz ◽  
Raymundo Domínguez-Cadena
Keyword(s):  
Forest Ecosystems ◽  
Baja California ◽  
Forest Type ◽  
Forest Types ◽  
Ecological Processes ◽  
Living Tree ◽  
Tree Diameter ◽  
Anthropogenic Stressors ◽  
Natural Factors ◽  
Ecological Changes

Understanding of the natural factors that lead to complex changes in forest ecosystems is limited. Worldwide, there are only a few forests as pristine and isolated as the Sierra de La Laguna in the southernmost range of the arid Baja California, Mexico. Its outstanding trait as a model system is that anthropogenic stressors are notably absent, which facilitates the study of natural ecological processes of the forest because separating human-induced ecological changes from natural ones is not a simple matter. In this study, we sampled sites and defined vegetation units on the basis of dominance of the canopy by the main tree species. We identified three forest types: the pine and encino forests that occupy the higher areas and the roble forest at lower elevations. For each living tree in the sampling plots, we measured height, canopy coverage per tree, diameter at breast height, as well as the amount of deadwood, leaf litter, and abundance of young trees. A succesional competition occurs between Pinus and Quercus sensu lato; we conclude that the encino forest represents a climax condition, the pine type represents an early succesional stage, and the roble forest type is a simple climax community.

Effects of human occupation on soil loss over the past two millennia in the Teotihuacan Valley, central Mexico

The Holocene ◽  
2021 ◽  
pp. 095968362110477
Author(s):  
María Lourdes González-Arqueros ◽  
Armando Navarrete-Segueda ◽  
Lorenzo Vázquez-Selem ◽  
Emily McClung de Tapia
Keyword(s):  
Land Use ◽  
Soil Erosion ◽  
Soil Loss ◽  
Geographical Information Systems ◽  
Soil Management ◽  
Geographical Information ◽  
Central Mexico ◽  
Human Occupation ◽  
Erosion Rates ◽  
The Face

Soil erosion is one of the greatest risks worldwide for land degradation. Avoiding it is one of the greatest socio-environmental and economic challenges within sustainable development in connection with food production and maintenance of soil functions in the context of climate change. This study will allow us to answer how long-term occupation dynamics influenced by notable changes in the landscape have led to soil erosion through time. We used Geographical Information Systems to apply the Revised Universal Soil Loss Equation to assess soil erosion on prehispanic and present occupation scenarios that differ in climate and land use management in the Teotihuacan Valley, central Mexico. We analyzed how a heterogeneous landscape and its occupation dynamics over the last two millennia were affected by soil erosion in order to identify which biophysical and anthropogenic components affect soil loss. The settlements extended during Aztec periods over previously forested hillslopes which caused an increase in erosion rates. The greatest soil loss occurred during the humid Aztec period, followed by the Modern period. The differences between average erosion and potential erosion of these periods demonstrate greater effectiveness in controlling erosion during the Aztec period. The most relevant factors involved were land use and soil management, followed by climate and support practices. Our results indicate that in the face of climatic variations, soil management has a significant impact, even greater than rain erosivity. Our results suggest that pre-Hispanic cultures in the highlands of central Mexico may have caused soil erosion at least at rates similar to or even higher than those at present. The comparisons of the scenarios enable researchers and decision makers to identify high-risk areas and to implement sustainable measures against soil erosion.

scholarly journals Quantifying ecological impacts of mass extinctions with network analysis of fossil communities

2018 ◽  
Vol 115 (20) ◽  
pp. 5217-5222 ◽  
Author(s):  
A. D. Muscente ◽  
Anirudh Prabhu ◽  
Hao Zhong ◽  
Ahmed Eleish ◽  
Michael B. Meyer ◽  
...  
Keyword(s):  
Network Analysis ◽  
Ecological Impact ◽  
Ecological Impacts ◽  
Ecological Change ◽  
Marine Animal ◽  
Mass Extinctions ◽  
Community Turnover ◽  
Ecological Changes ◽  
Extinction Events ◽  
Animal Communities

Mass extinctions documented by the fossil record provide critical benchmarks for assessing changes through time in biodiversity and ecology. Efforts to compare biotic crises of the past and present, however, encounter difficulty because taxonomic and ecological changes are decoupled, and although various metrics exist for describing taxonomic turnover, no methods have yet been proposed to quantify the ecological impacts of extinction events. To address this issue, we apply a network-based approach to exploring the evolution of marine animal communities over the Phanerozoic Eon. Network analysis of fossil co-occurrence data enables us to identify nonrandom associations of interrelated paleocommunities. These associations, or evolutionary paleocommunities, dominated total diversity during successive intervals of relative community stasis. Community turnover occurred largely during mass extinctions and radiations, when ecological reorganization resulted in the decline of one association and the rise of another. Altogether, we identify five evolutionary paleocommunities at the generic and familial levels in addition to three ordinal associations that correspond to Sepkoski’s Cambrian, Paleozoic, and Modern evolutionary faunas. In this context, we quantify magnitudes of ecological change by measuring shifts in the representation of evolutionary paleocommunities over geologic time. Our work shows that the Great Ordovician Biodiversification Event had the largest effect on ecology, followed in descending order by the Permian–Triassic, Cretaceous–Paleogene, Devonian, and Triassic–Jurassic mass extinctions. Despite its taxonomic severity, the Ordovician extinction did not strongly affect co-occurrences of taxa, affirming its limited ecological impact. Network paleoecology offers promising approaches to exploring ecological consequences of extinctions and radiations.

scholarly journals A review of ecological impacts of global climate change on persistent organic pollutant and mercury pathways and exposures in arctic marine ecosystems

2015 ◽  
Vol 61 (4) ◽  
pp. 617-628 ◽  
Author(s):  
Melissa A. Mckinney ◽  
Sara Pedro ◽  
Rune Dietz ◽  
Christian Sonne ◽  
Aaron T. Fisk ◽  
...  
Keyword(s):  
Climate Change ◽  
Sea Ice ◽  
Trophic Interactions ◽  
Global Climate Change ◽  
Global Climate ◽  
Marine Ecosystems ◽  
Arctic Sea Ice ◽  
Ecological Impacts ◽  
Health Concern ◽  
Ecological Changes

Abstract Bioaccumulative and biomagnifying contaminants, such as persistent organic pollutants (POPs) and mercury (Hg), have for decades been recognized as a health concern in arctic marine biota. In recent years, global climate change (GCC) and related loss of arctic sea ice have been observed to be driving substantial change in arctic ecosystems. This review summarizes findings documenting empirical links between GCC-induced ecological changes and alterations in POP and Hg exposures and pathways in arctic marine ecosystems. Most of the studies have reported changes in POP or Hg concentrations in tissue in relation to GCC-induced changes in species trophic interactions. These studies have typically focused on the role of changes in abundance, habitat range or accessibility of prey species, particularly in relation to sea ice changes. Yet, the ecological change that resulted in contaminant trend changes has often been unclear or assumed. Other studies have successfully used chemical tracers, such as stable nitrogen and carbon isotope ratios and fatty acid signatures to link such ecological changes to contaminant level variations or trends. Lower sea ice linked-diet changes/variation were associated with higher contaminant levels in some populations of polar bears, ringed seals, and thick-billed murres, but the influence of changing trophic interactions on POP levels and trends varied widely in both magnitude and direction. We suggest that future research in this new area of GCC-linked ecotoxicology should focus on routine analysis of ancillary ecological metrics with POP and Hg studies, simultaneous consideration of the multiple mechanisms by which GCC and contaminant interactions can occur, and targeted research on changing exposures and toxicological effects in species known to be sensitive to both GCC and contaminants.

Ecosystem models for management advice: An analysis of recreational and commercial fisheries policies in Baja California Sur, Mexico

2012 ◽  
Vol 228 ◽  
pp. 8-16 ◽  
Author(s):  
Andrés M. Cisneros-Montemayor ◽  
Villy Christensen ◽  
Francisco Arreguín-Sánchez ◽  
U. Rashid Sumaila
Keyword(s):  
Baja California ◽  
Commercial Fisheries ◽  
Baja California Sur ◽  
Ecosystem Models ◽  
Management Advice
Sign in / Sign up

Export Citation Format

Share Document