In Galapagos the pencil sea urchin Eucidaris thouarsii is a “corallivore” that greatly influences the ecological structure of Galapagos subtidal marine communities. While E. thouarsii does not commonly feed on coral elsewhere, in Galapagos it tends to diversify its diet to include large amounts of coral. Overfishing of lobsters – predators of Galapagos sea urchins – allows E. thouarsii populati...

Ecological and biological processes can change from one state to another once a threshold has been crossed in space or time. Threshold responses to incremental changes in underlying variables can characterize diverse processes from climate change to the desertification of arid lands from overgrazing. Simultaneously estimating the location of thresholds and associated ecological parameters can b...

Overgrazing is considered one of the key disturbance factors that results in alpine grassland degradation in Tibet. Grazing exclusion by fencing has been widely used as an approach to restore degraded grasslands in Tibet since 2004. Is the grazing exclusion management strategy effective for the vegetation restoration of degraded alpine grasslands? Three alpine grassland types were selected in T...

--This paper discusses the recreational and wildlife values of riparian habitats along the Rio Grande in western Texas (from El Paso to Del Rio). Several human activities have the potential or have in fact impacted on riparian resources in this region. These include: (1) irrigation diversions and stream channelization which greatly alter rates and amounts of water flow; (2) land flooding result...

In January 1986, a sea-urchm mediated deforestation began in C a m e l Bay, California. USA, near the center of the California sea otter's range. The deforestation occurred on an offshore rocky reef where depths range from l ? to > 30 m. Both purple (Strongylocentrotus purpuratus) and red (S. franciscanus) sea urchins were abundant and probably belonged to a cohort that settled in 1984. By Octo...

Introduced mammals are major drivers of extinction. Feral goats (Capra hircus) are particularly devastating to island ecosystems, causing direct and indirect impacts through overgrazing, which often results in ecosystem degradation and biodiversity loss. Removing goat populations from islands is a powerful conservation tool to prevent extinctions and restore ecosystems. Goats have been eradicat...

Biological invasions are major threats to biodiversity, with impacts that may be compounded by other forms of environmental change. Observations of high density of the invasive springtail (Collembola), Hypogastrura manubrialis in heavily grazed renosterveld vegetation in the Western Cape, South Africa, raised the question of whether the invasion was favored by changes in plant litter quality as...

The Qinghai-Tibetan Plateau is a very large land unit and an important terrestrial ecosystem within the Eurasian continent. Because of the harsh climate associated with the high altitude, alpine meadows on the plateau are susceptible to degradation from overgrazing. For this region, and for other alpine meadow pastures internationally, there is a need to define the sustainable stocking rate, to...

Regime shifts are abrupt transitions between alternate ecosystem states including desertification in arid regions due to drought or overgrazing. Regime shifts may be preceded by statistical anomalies such as increased autocorrelation, indicating declining resilience and warning of an impending shift. Tests for conditional heteroskedasticity, a type of clustered variance, have proven powerful le...

A research study was conducted in Mashuru Division of Kajiado District, Kenya with the objective of analyzing the types of vegetation degradation, their causes and their influence on rangeland condition and trend. The study was conducted through remote sensing tools, ground truthing, interviews, community workshop and literature. The results of the study showed that excessive use of the woody s...