Posted by: oikosasa | November 29, 2013

No more calls for the end of invasion biology?

Is invasion biology needed or not? In the Forum paper “A call for an end to calls for the end of invasion biology” by Daniel Simberloff and Jean Vitule continues the discussion, which Valery et al contributed too recently in Oikos. Below is the author’s summary of the paper:

The flood of damaging invasions by introduced species continues, with weekly reports on major invaders, such as Old World pigs in North and South America, Asian hornets in Europe, Asian ladybeetles in North America, Europe, and Africa, African grasses in the Americas and Hawaii, and African catfish in China and Brazil.  This rearrangement of global biogeography attracts public attention primarily when an invader does something dramatic and obvious that annoys humans, as when pigs ravage crops, hornets deliver painful stings, ladybeetles foul wine, grasses foster devastating fires, and catfish invade protected areas preying on native species used in traditional fisheries.  However, the myriad subtler impacts on individual species and on entire ecosystems exact a toll on human interests that is just beginning to be understood as the rapidly growing young science of invasion biology elucidates ever more mechanisms and outcomes of invasions.

The picture is not wholly bleak, however, as scientists develop means of preventing and managing invasions apace with understanding of the scope and scale of their consequences.  A plethora of mechanisms have been brought to bear successfully on damaging invasions, including biological control, chemical herbicides and pesticides, mechanical and physical measures, and a variety of clever specialized approaches tailored to the idiosyncrasies of particular invaders.  Notable recent advances include the use of pheromones to manage invasive sea lampreys in the North American Great Lakes, biological control insects, mechanical methods, chemicals, and inventive use of fire to cut back Australian paperbark in Florida, toxic microbeads to lower zebra mussel densities in water facilities, quick use of chemicals to eradicate infestations of an Australia marine algae in California and a Caribbean mussel in Australia, and eradication of introduced rats by poison baits on islands of ever-increasing size around the world.

Notable in these successes is that, in many cases, researchers did not wait to see what the impacts of the invaders would be, but acted quickly (e.g., the examples of the alga in California and the mussel in Australia).  Almost certainly the opportunity for eradication would have been lost had the scientists focused solely on impacts, rather than on the origin of the invader.  Another important point is that many of these successes (e.g., the paperbark in Florida, the sea lamprey in the Great Lakes, and many island rat populations) were achieved against longstanding invaders that had previously proven intractable.   Also, removal of well established invaders in these cases did not lead to unexpected harmful effects on any native species.

Finally, a few native species, particularly in the wake of various human impacts, behave like invasive non-native species, but harmful impact are far more likely for non-native than for native species.  The argument that fighting invaders and the traditional restoration focus on fostering native species are futile endeavors is contradicted by growing successes in restoration and invasion management.  

Figure 1. Jean Vitule holding a wild-caught African catifish Clarias gariepinus from an Atlanctica forest protected area in Guaraguaçu River, Brazil. Picture taken by Simone Umbria.

Figure 1. Jean Vitule holding a wild-caught African catifish Clarias gariepinus from an Atlanctica forest protected area in Guaraguaçu River, Brazil. Picture taken by Simone Umbria.

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