A cactus has been found growing in Australia with spines tough enough to penetrate tires! It’s been known to kill koalas, who develop infections because the spines are so difficult to remove.
The Hudson pear cactus is an invasive species native to Mexico. http://www.news.com.au/story/0,23599,23283785-2,00.html -via J-Walk Blog
Once spines of the hudson pear cactus penetrate the skin, they often require pliers to pull them out. It is potentially the worst cactus species to spread in Australia since prickly pear in the 1920s.
Primary Industries Department Biosecurity Queensland land protection officer Jodie Sippel said yesterday there was anecdotal evidence the cactus had caused a fatality at Lightning Ridge in NSW when a person fell into a clump of pear and had a heart attack.
The Hudson pear cactus is an invasive species native to Mexico. http://www.news.com.au/story/0,23599,23283785-2,00.html -via J-Walk Blog
Unfortunately, the cacti are NOT there as a result of nature, but rather people deliberately putting them there. Australia has a lot of problems with exotic (to them) flora and fauna being brought to the island continent and then running wild on their rather fragile native populations of plants and critters. Rabbits & pigs transplanted from Europe years ago are a big problem for one.
I don't know the specifics of the cacti, but they may have been brought in for the horticultural trade -- that has proven to a big problem for certain invasive plants (like Kudzu & Burning Bush) in the U.S. for example.
Get out the Round Up. Spray 'em all.
"Hudson pear was first detected in Australia in the Lightning Ridge area during the late 1960s. It is believed to have spread from a cactus nursery at Grawin. Some reports state that this process was aided by opal miners who deliberately used the plants to protect their diggings from nocturnal prowlers and thieves but these are unable to be verified."
There ya go. Some dopey nurseryman brought them in for people to put in their gardens.
Well, the article didn't say the offending nursery was in Grawin :-)