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Preface. Cane Toads

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Preface. Cane Toads ) ' +'* & %& January 1532, estuarine mudflats of Baia de Santos on the coast of Brazil. Portuguese sailors rowed ashore on a flooding tide, breached mangrove barricades and landed their commander Martim Afonso de Sousa, Governor of the Land of Brazil.1 In the Bay of Saints he sought blessings from on high and contemplated the magnitude of his tasks: chase away the French, harvest pau brasil (brazilwood [Caesalpinia echinata]), plant sugar cane and found a nation. Saints were beseeched, forests cleared, soils tilled, billets of cane trimmed, laid in rows and bur- ied. The giant toad aguaquaquan, known also as Bufo marinus, Rhinella marina and now colloquially as the cane toad, would look on as sugar cane plantings spread northwards into its homeland. January 2013, wet season, northern Australia. A savannah of sparse trees and resinous grasses scavenged sustenance from stony hills in the East Kimberley Ranges, Western Australia. A stately goanna flicked its forked tongue under a fire-blackened log and sensed food, sensed the vanguard of cane toads heading ever westwards across Aus- tralia’s tropical north, nocturnal invaders waiting out the heat of the day in the shade of the log. The goanna ate the toad in two swallows of its long neck, staggered a while, regurgitated a mucous lump, collapsed 1 Augeron & Vidal 2007, p. 23. $1 ( -), Figure 0.1 Redistribution of Bufo marinus from South America. (Redrawn and updated after Easteal 1981 and Zug & Zug 1979.) 1 + ! )!-),(' ( Figure 0.2 Redistribution of Bufo marinus from Hawai‘i. (Redrawn and up- dated after Easteal 1981 and multiple sources.) 1$ ( -), and died. Australia’s native fauna are unused to the toxins of foreign toads. These two seemingly unrelated events on different continents bracket almost 500 years of history for sugar cane and the cane toad. Over almost half a millennium, cane toads, assisted by generous man- kind, sugar cane farmers, scientists and the fortunes of war, colonised some 138 countries and islands,2 ending up as far from home as Flor- ida, Bermuda, Hawaii, Fiji, Guam, the Philippines and Japan. And if the introduction of sugar cane to the toad’s homeland was the Yin, the Yang was the introduction of cane toads to the island of Papua New Guinea, the ancestral home of sugar cane. Cane toads now occupy most of the tropical north of Australia – the largest contiguous population of cane toads outside their natural habitat of northern South America, Central America, southern Mexico and neighbouring islands. Toads were introduced by man to control pests in sugar cane be- cause ‘all portions of the cane plant are subject to destructive insect attack … species of white grubs devour the roots … wire worms may eatintothesettbuds…thestemisattackedbyborers…armyworms and other caterpillars and grasshoppers may devour the leaves … while mothborersmaydestroythegrowingpointofthecane’.3 In sugar cane plantations on the northern coast of South America, native cane toads were reputed to eat so many pests that 19th-century English and French plantation owners carried them from the mainland to their sugar es- tates in the Caribbean. And from there they were introduced around the sugar growing world. Today, it is hard to understand why toads were used to control pests because now we simply pick up a can of spray to kill an insect. The industry that produces today’s synthetic insecticides is a ‘child of the Second World War’.4 Its siblings, the chlorinated hydrocarbons and organic phosphates now banned from general use, delivered spectacu- larly effective pest control – at a cost to the environment. Before these new poisons were invented, agricultural pesticides were crude, nasty, and ineffective products like tar, copper, sulphur, lead and arsenic com- pounds. Without effective pest control, farmers and gardeners stim- 2 Lever 2001. 3 Kerr & Bell 1939, p. 172. 4 Carson 1968(1962), p. 31. 1$$ + ! )!-),(' ( ulated a worldwide currency in agents of ‘biological control’. These agents included such ‘beneficial’ organisms as carnivorous ladybirds, parasitic wasps and flies, insectivorous birds, cactus-hungry moths, vo- racious mongoose and omnivorous toads. Sugar cane scientists were among the busiest traders in this currency but, although these agents were biological, their promoters had no control over their behaviour. The emergence of the cane toad as an agent of biological control has its foundations in the unregulated distribution and release of ‘be- neficial’ organisms. That is why this story details the parade of beetles, wasps and flies that were released,ntested, u into sugar cane fields; it helps us to understand the actions of scientists responsible for the later release of the cane toad into unsuspecting environments. In 1935 sugar scientists released the cane toad into sugar cane fields in Queensland on Australia’s tropical east coast. The release was sup- ported by cane growers, leading scientists, and politicians including the prime minister of Australia. At the time, none but a lone voice thought it possible that an exotic amphibian could traverse this continent’s arid outback – often too tough for men – let alone breed and colonise new environments. It took 74 years for toads to traverse Australia’s trop- ical north to arrive at the Western Australian border. Generation after generation of toads hopping in an evolutionary relay, grandparent to parent to offspring, over and again, more than 2,400 km across hotand mostly arid landscapes. Cane toads failed spectacularly in their allotted task in the cane fields. Their task was to eat the adults of soil-dwelling beetle larvae that ate the roots of sugar cane, and thereby control populations of the pest. They failed in Caribbean lands,is in Hawai‘i and in Australia. Cane toads will eat almost anything that moves and is small enough to swallow, but their reputation in targeted pest control was gained through erroneous deduction, desperation and wildly optimistic ex- trapolation. To control populations of soil-dwelling larvae by eating airborne beetles is a tall order for any predator no matter how hungry. Canetoadscouldnevercontrolpopulationsofthebeetlestheywere tasked with. The great leaps forward in global distribution of toads were done with the help of men and women bereft of ideas about how else to con- trol the pests that were eating their sugar cane or garden crops. They were well respected and well intentioned figures in their communities, 1$$$ ( -), not villains out to colonise the country with a toxic alien amphibian. But their stories are a litany of desperation – a desperation that caused myopia. And myopia caused errors that were compounded infinitely by the extraordinary breeding and colonising capabilities of the cane toad. The resulting invasion of many territories, including northern Australia, is a sad reflection on those who championed the toad, on the times, the state of science and the paucity of quarantine procedures that allowed its importation and release. Thisstoryisaboutgoodintentionsthatturnedbad.Itisataleof good-ideas-at-the-time, a tale of unintended consequences and, most of all, a tale of simple acts leading to catastrophic outcomes. This story about human nature has modern parallels. It is about scientists so com- mitted to helping solve a problem that they are blinkered from viewing adverse impacts; committed to serving their country, their leaders and their benefactors – the industry that employed them. There is no blame to apportion – just lessons to learn from the toad’s tale. And, as the tale shows, we come perilously close to repeating the mistakes of the past. 1$/.
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