想象一个山间湖泊，你每走一步，就有几十只青蛙跳入水中。这曾是加利福尼亚州内华达山脉的常态。据美联社在KQED上的报道，研究人员罗兰·纳普记录了内华达山脉黄腿蛙的回归。他2016年发表在《美国国家科学院院刊》上的研究发现，公园内的青蛙数量在20年内增加了七倍。认识这种青蛙这种青蛙长度刚超过3英寸。
Imagine a mountain lake where each step you take causes dozens of frogs to leap into the water. That used to be the rule in California’s Sierra Nevada. According toan Associated Press report on KQED, researcher Roland Knapp documented the return of the Sierra Nevada yellow-legged frog. His 2016 study, published in the Proceedings of the National Academy of Sciences, found the number of frogs in the park had increased sevenfold in 20 years. Meet the frogThe frog is just over 3 inches long.
它的显著特征是后腿下方的颜色。它曾是内华达山脉最常见的两栖动物。国家公园管理局表示，游客过去经常在湖岸看到成百上千只。蝌蚪可以成千上万地堆积在一起。青蛙还捕食昆虫和其他小动物，因此是食物链的重要组成部分。没有鱼的湖泊海拔4000英尺以上的约塞米蒂湖泊和溪流天然没有鱼。公园管理局官员表示，冰川形成了陡峭的瀑布，阻止了鱼类逆流而上。
It is notable for the color under its hind legs. It was once the most common amphibian in the Sierra Nevada. The National Park Service says visitors regularly saw hundreds along lakeshores. Tadpoles could pile up by the thousands. The frogs also preyed on insects and other small animals. That made them an important part of the food chain. Lakes without fishYosemite lakes and streams over 4,000 feet in elevation were naturally devoid of fish. Park service officials say the glaciers created steep waterfalls that blocked fish from swimming upstream.
结果，青蛙在没有鱼的环境中进化，也没有对这些捕食者的防御能力。然后鳟鱼来了约塞米蒂地区的放鱼活动始于1877年，这是有记录的第一年，并持续到1990年。起初，鱼是人工搬运的。后来用骡子运输。最终飞机投放了鱼。鱼吃掉了青蛙，并与它们争夺食物。博物学家早在20世纪20年代就开始写关于这个问题的文章。
As a result, the frogs evolved without fish around and without defenses against these predators. Then came the troutFish stocking in the Yosemite area began in 1877, the first recorded year, and continued through 1990. At first, the fish were carried by hand. Later they were hauled by mules. Planes eventually stocked them. The fish ate frogs and competed with them for food. Naturalists had been writing about the problem as early as the 1920s.
美联社报道指出，青蛙种群大约在一个世纪前开始崩溃。致命真菌疾病后来出现。它被称为壶菌病，由一种真菌引起。公园管理局表示，这种真菌自20世纪70年代以来已在整个内华达山脉传播。它导致数百个青蛙种群灭绝。它已传播到约塞米蒂大部分黄腿蛙种群。
Frog populations started crashing about a century ago, the AP report notes.A deadly fungusDisease came later. It is called chytridiomycosis, and a fungus causes it. The park service says it has spread throughout the Sierra Nevada since the 1970s. It has led to the extinction of hundreds of frog populations. It has spread to most of the yellow-legged frog populations in Yosemite.
科学家指出，鳟鱼和疾病先后导致这种青蛙从内华达山脉约 90% 的原生栖息地消失。复苏的开始优胜美地从 1972 年开始逐步停止投放鱼苗。到 1975 年，大多数湖泊不再投放。到 1990 年，所有投放均已结束。报告称，在部分湖泊停止投放有助于青蛙复苏。公园还于 2007 年开始从部分湖泊清除鱼类。目标是将约 250 个有鱼湖泊中的 25 个恢复为无鱼状态。
Scientists note that trout and then disease took the frog out of about 90% of its native habitat in the Sierra. The comeback startsYosemite began to phase out stocking in 1972. Most lakes were no longer stocked by 1975. By 1990, all stocking had ended. Ending stocking in some lakes helped the comeback, the report said. The park also started removing fish from some lakes in 2007. The goal is to return 25 of about 250 fish-bearing lakes to fishless conditions.
部分青蛙种群似乎正在适应这种真菌。它们在感染后仍能存活。漫漫长路克纳普称这种反弹是一个重要里程碑。他说，青蛙要恢复到过去的数量还有很长的路要走。同一份报告称，反弹仅限于优胜美地，该公园拥有该青蛙在内华达山脉历史栖息地的 13%。在其分布范围的其他地方，青蛙依然稀少。它仍被列为联邦濒危物种受到保护。
Some frog populations seem to be adapting to the fungus. They survive when infected.A long journeyKnapp called the rebound an important milestone. He said the frog has a long way to go to reach its old numbers. The same report said the rebound was limited to Yosemite, which holds 13 percent of the frog’s historical habitat in the Sierra. Elsewhere in its range, the frog remained scarce. It is still protected as a federally endangered species.
如今，优胜美地仍有约 250 个水体和 800 英里河流溪流含有非本地鱼类。复苏的意义公园水生生态学家罗布·格拉索表示，物种很少能从濒危名单中除名。这种青蛙表明，即使是极度濒危的物种也能复苏。格拉索希望青蛙将来能从名单中除名。研究人员指出，更好的管理和青蛙对真菌的抵抗力或许能扭转其他地方两栖动物的衰退。据公园管理局称，公园内许多地点仍可垂钓。大自然与游客可以共享同一个公园。
Today, some 250 water bodies and 800 miles of rivers and streams in Yosemite still contain non-native fish. What the recovery meansRob Grasso, the park’s aquatic ecologist, says species rarely come off the endangered list. This frog shows that even a severely imperiled species can recover. Grasso hopes the frog could one day come off the list. Researchers note that better management and the frog’s resistance to the fungus may be able to reverse amphibian declines elsewhere. Fishing is still available at many sites in the park, according to the park service. Nature and visitors can share the same park.