Invasive species research
Climate change and the introduction of alien plants are considered major threats to global biodiversity, as they affect ecosystem processes including carbon assimilation and fire by affecting vegetation flammability and habitat suitability for indigenous species. Such effects are of particular concern in pristine ecosystems, which are essential repositories of biodiversity.
Mediterranean-climate ecosystems, such as the fynbos and succulent karoo biomes of southern Africa , are especially sensitive to changes in biodiversity. Both biomes are global biodiversity hotspots due to their exceptionally high species richness and endemism, rapid spread of urbanization, agriculture and alien species, which have contributed to numerous species extinctions. Therefore, they are especially vulnerable to biodiversity loss and distributional range changes with future warming and aridity trends.
Apart from woody invasive species, which currently occupy about 36% of pristine fynbos ecosystems not transformed by urbanization and agriculture, alien grasses are emerging as a potential cause for concern. This is especially so for the wildflower diversity which underpins the growing and lucrative nature-based tourism industry, particularly in the succulent karoo.
The invasion of alien annual grasses into landscapes from contaminated road verges and agricultural lands is facilitated by the transport of their seeds on the hide of grazing animals, dung of domestic livestock and wildlife. Invasion is exacerbated by rangeland deterioration caused by ploughing, vegetation clearing and burning, soil nutrient enrichment from fertilizer runoff and nitrogen-fixing leguminous species, and rising atmospheric CO 2 levels which are expected to increase the competitive dominance of alien annual C 3 grasses in indigenous C 4 -dominated grasslands.
Current research examines the impacts of invasive alien grasses on ecosystem diversity under current and future climate change scenarios. It is focused in three directions:
Bioclimatic modeling
Click to enlarge figure above
This work involves extracting geographical distribution records for all listed alien grass species from the SAPIA, Acocks and PRECIS databases and interfacing these a digitized ? -version of the South African vegetation map, a meteorological database and a database of rare and endangered taxa. Statistical matches applying Generalized Additive Models are made between climate variables and the boundaries of alien species' distributions. These are then used to predict changes in geographical distributions of alien grasses under different future climate scenarios and their impact on the indigenous flora - particularly rare and endangered taxa.
Experimental validation
Click image to enlarge
This research involves testing modeled climate change impacts on the indigenous and alien flora using passive (open-top chambers) and active (infra-red) heating systems located in natural (field), semi-natural (microcosms) and artificial (greenhouse) environments.
Management
This research involves testing the cost-effectiveness of various labour-intensive strategies, i.e. clearing, mowing, light and intense burning, herbicide application, involving local impoverished communities in South Africa for managing alien invasive grass infestations to conserve biodiversity.
For more information, contact Charles Musil or Fatima Parker-Allie.
Photo and illustration credits : Parker-Allie and Musil
|
