在美国西南部的一条沙漠河流中，一种小型甲虫和一种小型鸟类的命运紧密相连。卫星照片显示，在引入甲虫以啃食一种入侵灌木后，这种稀有鸣禽所需的栖息地减少了90%。这一减少背后的原因告诉我们，在不引发另一个问题的前提下解决一个问题，有多么困难。
In one desert river in the Southwest, there is a small bug and a small bird that are intertwined together. From satellite photos, it is found that when beetles were introduced to eat an invasive bush, 90 percent of the habitat required by the rare songbird has been reduced. The reason behind such reduction tells us how difficult it is to solve one issue without causing another.
这种鸟是西南柳鹟，一种濒危鸣禽，每年5月至9月生活在美国西南部的河流和溪流中。这种鸟在离地面10至13英尺（约3至4米）高的纠缠植被中筑巢，通常靠近水源。根据詹姆斯·R·哈滕在2016年美国地质调查局报告中引用的2007年调查数字，共有约1299个领地，分布在288个地点。解决一个问题却引发另一个问题盐生柽柳（Tamarisk）在一百多年前被引入美国，现已占据西部所有的河滨地带，这种鸟经常利用它筑巢。
The bird in question is the Southwestern willow flycatcher, an endangered songbird that spends from May to September in the rivers and streams of the Southwestern region. This bird builds its nest in tangled vegetation 10-13 feet off the ground, often near water sources. The 2007 survey numbers, as cited in the 2016 U.S. Geological Survey report by James R. Hatten, total some 1,299 territories in 288 sites.A solution to one problem causes anotherTamarisk, which was introduced into the country over a hundred years ago, has come to occupy all riparian areas in the West, and the birds often use it for nesting purposes.
2001年，美国农业部在六个州的10个地点引入盐生柽柳叶甲，试图遏制该植物的蔓延。幼虫啃食叶片，反复取食会在约五年内使植物枯死。这就引出一个问题：筑巢于这种受威胁植物中的鸟类会发生什么？美国地质调查局的报告利用陆地卫星影像和在亚利桑那州建立的栖息地模型探讨了这一问题。栖息地模型识别出与柳鹟栖息地相似的植被；报告称之为“预测栖息地”，而非实际巢址。
In 2001, the U.S. Department of Agriculture introduced tamarisk leaf beetles at 10 sites in six states in an effort to curb the plant’s spread. The larvae eat the leaves, and repeated feeding kills the plant in about five years. That begs the question: What would happen to a bird nesting in the plant under threat? The U.S. Geological Survey report tackles the issue, using Landsat satellite images and habitat models created in Arizona. The habitat models identify vegetation that appears similar to flycatcher habitat; the report calls this predicted habitat rather than actual nests.
模型的准确性评估发现，使用40%概率阈值，该模型正确分类了2014年记录的758个西南柳鹟领地中的88%。维京河数据说明什么该案例研究考察了内华达州和亚利桑那州下游维京河一段长65公里（约40英里）的河段。
The model’s accuracy assessment found that it correctly classified 88% of 758 Southwestern willow flycatcher territories recorded in 2014, using a 40% probability threshold. What the Virgin River numbers meanThe case study examined a 65-kilometer (about 40-mile) stretch of the lower Virgin River in Nevada and Arizona.
根据美国地质调查局（USGS）2016年发布的一份报告，盐生木叶甲最早于2008年在河流沿岸被观测到，但栖息地时间序列直到2011年才显示出其影响。最大的栖息地衰退发生在2013年至2015年期间。报告指出，从1986年到2011年，预测的黄鹟栖息地平均为700.3公顷，约合1730英亩，尽管年度估算值在大约356至1044公顷之间波动。从2013年到2015年，平均值降至88公顷，仅相当于历史平均值的12.6%。
Tamarisk leaf beetles were first observed along the river in 2008, but the habitat time series did not show their effects until 2011, according to a 2016 U.S. Geological Survey report. The largest habitat declines occurred between 2013 and 2015. From 1986 to 2011, predicted flycatcher habitat averaged 700.3 hectares, or about 1,730 acres, although annual estimates fluctuated between roughly 356 and 1,044 hectares. From 2013 to 2015, the average fell to 88 hectares, equivalent to 12.6% of the historical average, the report found.
对比两个单独年份显示了变化的规模。根据美国地质调查局报告，下维尔京河沿岸预测的黄鹟栖息地从2010年的937公顷降至2015年的87公顷，下降了90.7%。在2010年绘制的栖息地中，到2015年有94.2%已消失，仅5.8%得以保留。在预测栖息地消失的区域，一种基于卫星的植被绿度指标也下降了近49%。损失情况在河流各段有所不同：距离米德湖国家休闲区最近的河段在2010年拥有618公顷预测栖息地，到2015年失去了其中的99.6%，而最上游的河段则从不到1公顷的基线值增加了栖息地。
Comparing two individual years shows the scale of the change. Predicted flycatcher habitat along the lower Virgin River fell from 937 hectares in 2010 to 87 hectares in 2015, a 90.7% decline, according to the USGS report. Of the habitat mapped in 2010, 94.2% was lost by 2015, while 5.8% persisted. A satellite-based measure of plant greenness also declined by nearly 49% in areas where predicted habitat disappeared. The losses varied across the river: the zone nearest Lake Mead National Recreation Area had 618 hectares of predicted habitat in 2010 and lost 99.6% of it by 2015, while the farthest upstream zone gained habitat from a baseline of less than one hectare.
该研究还模拟了甲虫尚未到达的河流。通过将绘制在图上的盐生木绿度值减半——这一减幅取自维尔京河的结果——模型预测下科罗拉多河预测栖息地将下降33.5%，亚利桑那州上希拉河预测栖息地将下降53.1%。报告发布时，预计甲虫将在几年内抵达这两条河流。一些管理者已在采取行动：在希拉河沿岸，人们正在清除盐生木并种植本地柳树；在科罗拉多河沿岸，美国垦务局正在用本地植被取代农业种植园。这些结果存在局限性。
The study also simulated rivers the beetles had not yet reached. By cutting the greenness values of mapped tamarisk in half, a reduction drawn from the Virgin River results, the model projected a 33.5 percent drop in predicted habitat along the lower Colorado River and a 53.1 percent drop along the upper Gila River in Arizona. When the report was published, beetles were expected to arrive on both rivers within a few years. Some managers were already preparing: along the Gila, tamarisk was being removed and replaced with native willows, and on the Colorado, the Bureau of Reclamation was replacing agricultural plantations with native vegetation. There are limitations to these results.
维京河的破坏非常严重，很大程度上是因为整条河沿岸都生长着盐生柽柳。哈滕还指出，本地物种较多的区域破坏程度会较轻。该模拟工具无法预测鸟类每年将使用哪些地块。此外，这两次模拟所用的植被地图尚未经过准确性验证。然而，其更深远的影响远不止这一种鸟类。
The destruction in the Virgin River was extensive, in large part because the entire river has tamarisk along it. Hatten also states that areas with more native species will experience less destruction. The simulation tool cannot predict which patches of land the birds will use each year. Moreover, the two simulations utilized vegetation maps that have not been validated for their accuracy. However, the larger implication extends beyond one bird.