Search the SPREP Catalogue

Questions: Do past disturbance, soil nutrients, or species diversity predict the invasion success of the alien tree Pittosporum undulatum in an island montane rain forest? What are the consequences of its invasion for forest composition and species diversity? Location: Blue Mountains, Jamaica. Methods: Censuses of trees ? 3 cm DBH in permanent plots in four sites within ca. 7 ha; 1974–2004 (intensive sites) and in 16 plots within 250 ha; 1990–2004 (extensive plots). Results: Pittosporum was unrecorded in the intensive sites before a severe hurricane in 1988: by 2004 all four sites were invaded. Pittosporum had invaded 25% of the extensive plots in 1990 and 69% in 2004, where its basal area increased from 0.5 ± 0.4 (SEM) m2.ha?1 in 1990 to 2.8 ± 1.3 m2.ha?1 in 2004. It had zero stem mortality and diameter growth rate exceeded that of native species fourfold. Pittosporum's basal area in the extensive plots in 2004 was positively related to the stand basal area damaged in the 1988 hurricane and negatively related to soil N concentrations. Pittosporum invasion was unrelated to stand-level tree species diversity in the extensive plots but as its basal area increased over time the basal area of native species and stand-level diversity declined. Conclusions: There are no obvious functional attributes of Pittosporum unrepresented in the native tree flora although it has high photosynthetic efficiency compared with native trees. More widespread invasion of these forests by Pittosporum seems inevitable since hurricanes, which accelerated the invasion, affect these forests frequently.

Disturbances are a primary facilitator of the growth and spread of invasive species. However, the effects of large-scale disturbances, such as hurricanes and tropical storms, on the broad geographic patterns of invasive species growth and spread have not been investigated. We used historical aerial imagery to determine the growth rate of invasive Phragmites australis patches in wetlands along the Atlantic and Gulf Coasts of the United States. These were relatively undisturbed wetlands where P. australis had room for unrestricted growth. Over the past several decades, invasive P. australis stands expanded in size by 6–35% per year. Based on tropical storm and hurricane activity over that same time period, we found that the frequency of hurricane-force winds explained 81% of the variation in P. australis growth over this broad geographic range. The expansion of P. australis stands was strongly and positively correlated with hurricane frequency. In light of the many climatic models that predict an increase in the frequency and intensity of hurricanes over the next century, these results suggest a strong link between climate change and species invasion and a challenging future ahead for the management of invasive species.

The hawksbill turtle gets its common English name from its sharp beak-like mouth which distinguishes it from other turtle species

The evolution and expansion of the human species over the past few hundred thousand years, an infinitesimal fraction of planetary time, now sees us as the dominant life form on Earth. We are dominant because of our intelligence and adaptability, and our need to constantly strive for newer and better ways of doing things. But there are now six billion of us, predicted to increase to 8-10 billion by 2050, and our domination of the planet is paralleled by the massive impact that we have had on the Earth's ecosystems. A recent mapping of the human footprint on the planet has concluded that more than 80% of the Earth's land surface is directly influenced by humans. We consume 40% of the Earth's net primary productivity, 35% of oceanic shelf productivity and 60% of freshwater runoff. As a result, remaining natural landscapes are rapidly being modified and the Earth's biological diversity continues to decline at an alarming rate. The Millennium Ecosystem Assessment (MEA) has found that in the last several decades 20% of the world’s coral reefs were lost and 20% degraded, while 35% of mangrove area has been lost. The MEA also concluded that humans have likely increased the species extinction rate by as much as 1,000 times over background rates typical throughout Earth's history.