原本被引入澳大利亚用于帮助农场发展的树种，如今却成了该国最为棘手的外来杂草之一。北领地政府称，这种带刺相思树最初是作为遮阴树和饲料树引入澳大利亚的。如今，它已蔓延至超过660万公顷的土地上，并被政府列为“具有全国性危害的外来杂草”，这一称号专门授予那些危害极大的外来杂草。
A tree brought in to help Australian farms has become one of the country's toughest weed problems. The Northern Territory Government says prickly acacia was first introduced to Australia as a shade and fodder tree. It now infests more than 6.6 million hectares of the country and is listed by the government as a Weed of National Significance, a national label applied to weeds with major impacts.
人们为何种植这种树该树种原产于非洲热带及亚热带地区、巴基斯坦、印度和缅甸。根据克里蒂科斯等人于2003年在《应用生态学杂志》上发表的研究，19世纪90年代，人们出于遮阴、提供饲料及观赏目的将其引入澳大利亚。到1926年，这种树已在昆士兰州的鲍文与罗克汉普顿地区扎根。后来它又被当作绵羊的遮阴树与饲料来源进行销售，尽管当时人们早已知道它在养牛区会造成诸多问题。
Why people planted itThe tree is native to tropical and subtropical Africa, Pakistan, India and Myanmar. It came to Australia in the 1890s for shade, fodder and ornamental purposes, according to a 2003 study by Kriticos and colleagues in the Journal of Applied Ecology. By 1926, it was established in the Bowen and Rockhampton districts of Queensland. It was later sold as a source of shade and feed for sheep, although it had long been known as a problem in cattle country.
直至1957年3月9日，该树种才被正式列为有害植物，而那时它早已在昆士兰州的中部和西部地区广泛蔓延。
It was not declared noxious until March 9, 1957, by which time it had spread across much of central and western Queensland, the paper said.
为何能如此迅速扩散牛群是这种杂草扩散的重要因素。政府指出，其种子会附着在牛的毛发与蹄子上，还能完整通过牛的消化系统排出。牲畜会将种子从母树处带到其他地方。种子通过动物体内排出大约需要六天时间。此外，水流也能携带这些种子。克里蒂科斯的研究指出，这种植物主要通过牲畜食用并排泄种子的方式跨越牧场边界扩散。一旦扎根，它便会在水源附近迅速生长，挤占本地植物的生存空间。这种树最高可长到10米，形成茂密的灌丛。
How it spreads so wellCattle are a large factor in its spread. The government says the seeds are carried on the hair and hooves of cattle and also pass through a cow's digestive tract intact. Livestock can carry seeds away from the parent tree. It can take six days for seeds to pass through an animal. The seeds can also be carried by water. The Kriticos study says the plant moves across a paddock boundary mainly through livestock eating and defecating the seeds. Once established, the tree flourishes along watercourses and outcompetes native plants. It can reach up to 10 m in height and forms dense thickets.
对土地与野生动植物的影响据政府介绍，大面积的杂草滋生会降低牧草产量；茂密的灌丛则增加牲畜驱赶难度，并阻碍牲畜获取水源。克里蒂科斯的研究还指出，这种杂草会延长牲畜驱赶时间、增加相关成本，并加剧土壤侵蚀。
What happens to the land and wildlifeAccording to the government, dense infestations reduce pasture production, and thickets make mustering harder and limit stock access to water. The Kriticos paper also notes that the weed increases mustering times and costs, and increases soil erosion.
澳大利亚的乡土动植物也深受其害，因为这种灌木丛将它们排挤出去，减少了生物多样性。荆棘也是一个问题，因为它们会刺破车辆轮胎并对动物造成伤害。政府表示，这种杂草威胁着澳大利亚北部大部分地区的农业和环境，包括北领地的巴克利高原。它还会进一步蔓延吗？研究人员使用气候模型来预测这种树可能生存的区域。
Native plants and animals also suffer as the thickets force them out and reduce biodiversity. The thorns are also a problem, as they can puncture vehicle tires and cause injury to animals. The government says the weed threatens farming and the environment across much of northern Australia, including the Barkly Tablelands in the Northern Territory. Could it spread even furtherResearchers used a climate model to predict where the tree might be able to live.
他们发现，在当前条件下，该物种的潜在分布范围远远大于其目前的分布范围。在他们的模型中，适宜或高度适宜的栖息地覆盖了澳大利亚三分之一以上的面积。作者还表示，气候变化可能会扩大这一区域。他们提到，该模型忽略了影响这种树分布的其他因素，如土壤类型和土地利用方式。对此能做些什么？该论文提出，简单的牧场隔离——让牲畜在转移前有时间排出种子——可能有助于限制这种植物的分布范围。
They found that the potential range of the species under present conditions is far greater than its present distribution. In their model, suitable or highly suitable habitat covered over one third of Australia. The authors also said climate change is likely to expand the area. They mentioned that the model ignores other factors affecting the tree's distribution, like soil type and land use. What can be done about it? The paper suggests that simple paddock quarantine, which gives livestock time to drop seeds before moving, may help limit the plant’s range.
政府也建议采取类似措施，例如用围栏将牲畜与成熟的豆荚隔开，并对从受侵染地区转移的动物进行隔离。研究还发现，早期行动加上每年一次的防治计划能带来最佳的投资回报。文中指出，处理这种植物的最佳季节是3月至5月。昆士兰州的研究人员还探索了昆虫等生物防治方案。综合来看，这个故事说明了一棵为遮荫和饲料而种植的树如何变成了一个长期的问题。
The government also recommends similar measures, such as fencing stock away from mature pods and quarantining animals moved from infested areas. Research has found that early action coupled with a yearly control program offers the best return on investment, it says. The best season to treat the plant is identified as March to May. Researchers in Queensland have also explored biocontrol options such as insects. Taken together, the story shows how a tree planted for shade and feed became a lasting problem.