Indicators of Catchment Condition in the Intensive Land Use Zone of Australia – Feral animal density

\n\nIt should be noted that this data is now somwhat dated!\n\nFeral animals impact on catchment condition by added grazing pressure,\ncompetition with native animals and by increased ground and water disturbance.\nFeral animals can also host and distribute diseases such as Brucellosis and\nmange. Rabbits and goats are renowned for their grazing impact, and including\npigs, can cause severe ground disturbance leading to erosion. Foxes and cats\nare predatory on many native species and also transmit diseases. Buffalo cause\nmuddying of waterways and can harbour Brucellosis. Buffalo, horses and goats\ncan also assist the spread of weeds.\n\nFeral animal density is an indicator of the extent to which Australia has been\ncolonised by a range of exotic fauna species. Native species numbers and\ndistributions have declined through direct predation, such as by foxes and\ncats, overgrazing by rabbits and goats to changing habitat conditions through\ncompetition for available resources. This issue is difficult to address at a\ncatchment scale due to animal mobility.\n\nRegional/national strategies are required (eg. use of calicivirus to wipe out\nrabbits). The main areas of Australia with relatively high feral animal counts\nare Gippsland and the mountains of southern NSW. The Victoria River Downs (NT)\nalso shows with high feral animal density. Moderate to poor condition is\notherwise indicated throughout most of eastern Australia and in the north of\nW and in the Northern Territory. Feral animal density is generally low in\nmost parts of Tasmania, South Australia, and Western Australia and in the\nRiverina District of New South Wales. The ABARES/CSIRO feral animal coverages\nwere used, which date from the late 1980s.\n\nThe scale of mapping is 1:25M. These maps give qualitative spatial\ndistributions for 22 feral species. Four classes of feral animal density were\ndefined (high, medium, low and none) and assigned a numerical value (3, 2, 1\nand 0). The density values for each species were added for all species, giving\na relative feral animal rating. Given the low resolution of the feral animal\ncoverages, only a broad regional picture is possible. Data reliability is\npoor.\n\nData are available as:\n\n * continental maps at 5km (0.05 deg) cell resolution for the ILZ;\n * spatial averages over CRES defined catchments (CRES, 2000) in the ILZ;\n * spatial averages over the AWRC river basins in the ILZ.\n\nSee [further metadata](http://data.daff.gov.au/anrdl/metadata_files/pa_iccilr9ab\n__07121axx.xml) for more detail.\n\n

需注意，本数据集现已较为陈旧！

野化动物（feral animals）可通过施加放牧压力、与本土动物竞争以及加剧地面与水体扰动，对集水区的健康状况产生不利影响。野化动物还可携带并传播布鲁氏菌病（Brucellosis）和疥癣（mange）等疫病。兔与山羊以其显著的放牧影响而闻名，而猪同样可引发严重的地面扰动，进而导致水土流失。狐与猫会捕食众多本土物种，同时也会传播疫病。水牛会造成水道淤积浑浊，且可携带布鲁氏菌病。水牛、马与山羊还会助力杂草的扩散。

野化动物密度可作为澳大利亚被一系列外来动物类群入侵程度的指示指标。本土物种种群数量与分布范围之所以出现缩减，原因包括狐与猫的直接捕食、兔与山羊的过度放牧，以及因争夺有限资源而引发的栖息地条件改变。由于动物具有移动性，该问题在集水区尺度下难以得到有效治理。

需制定区域/国家级防控策略（例如利用杯状病毒（calicivirus）灭杀兔种群）。澳大利亚野化动物种群密度相对较高的核心区域为吉普斯兰（Gippsland）与新南威尔士州南部山地，北领地的维多利亚河唐斯（Victoria River Downs, NT）同样呈现较高的野化动物密度。除此之外，澳大利亚东部大部分区域、西澳大利亚州北部以及北领地的集水区状况均处于中等至较差水平。塔斯马尼亚州、南澳大利亚州、西澳大利亚州的大部分区域，以及新南威尔士州的里弗赖纳区（Riverina District），其野化动物密度普遍较低。本数据集采用了澳大利亚农业与资源经济科学局（ABARES）与联邦科学与工业研究组织（CSIRO）的野化动物覆盖数据，其采集时间可追溯至20世纪80年代末。

本数据集的制图比例尺为1:2500万。该套地图对22种野化动物的空间分布进行了定性描述。研究人员将野化动物密度划分为四个等级（高、中、低、无），并分别赋值为3、2、1、0。将各物种的密度数值进行累加，即可得到相对野化动物危害评级。由于野化动物覆盖数据的分辨率较低，仅能呈现较为粗略的区域格局，且数据可靠性较差。

数据集可通过以下形式获取：
* 针对内陆陆地区域（ILZ）制作的、分辨率为5km（0.05°）的大陆级栅格地图；
* 内陆陆地区域（ILZ）范围内由CRES划定的集水区的空间平均数据（CRES，2000）；
* 内陆陆地区域（ILZ）范围内由澳大利亚水资源委员会（AWRC）划定的流域的空间平均数据。

详细信息可参阅[补充元数据](http://data.daff.gov.au/anrdl/metadata_files/pa_iccilr9ab__07121axx.xml)。