除非我们应对气候变化，否则约书亚树将在2070年面临灭绝

除非我们应对气候变化，否则约书亚树将在2070年面临灭绝

Dramatic-looking Joshua trees have survived since the Pleistocene era, about 2.5 million years. Now, because of climate change, their extinction is looming.

外表引人注目的约书亚树自更新世以来存活了大约250万年。现在，由于气候变化，它们的灭绝迫在眉睫。

In a new study, researchers and a team of volunteers gathered data on more than 4,000 trees in Joshua Tree National Park in southern California. They discovered the trees have been migrating to parts of the park with higher elevations that offer cooler weather and more moisture in the ground — safe zones for the trees. Adult trees in drier, hotter areas aren't producing as many young plants, and those that are produced aren't surviving.

在一项新的研究中，研究人员和一组志愿者收集了南加州约书亚树国家公园4000多棵树的数据。他们发现，这些树木已经迁移到公园中海拔较高的地区，那里的天气更凉爽，地面湿度更大，是树木的安全地带。在更干燥、更炎热的地区，成树不能生长出那么多的幼树，那些生长出来的也不能存活。

Photo: Esther Lee/Flickr

Their findings were published in the journal Ecosphere.

他们的发现发表在《生态圈》杂志上。

Considering the predicted impacts of climate change, the researchers estimated how many of these safe zones — or "refugia" — would survive. They predict that in the very best-case scenario, if major steps are taken to lower carbon emissions, about 19% of the trees will remain after 2070.

考虑到气候变化的预测影响，研究人员估计了这些安全区(或“避难所”)中有多少能够生存下来。他们预测，在最理想的情况下，如果采取重大措施降低碳排放，大约19%的树木将在2070年后保留下来。

However, if things continue as they are and there's no attempt to reduce carbon emissions and temperatures continue to rise, only .02% of the trees will remain.

然而，如果事情继续这样下去，没有任何减少碳排放的尝试，气温继续上升，那么只有0.02%的树木会保留下来。

"The fate of these unusual, amazing trees is in all of our hands," lead study author Lynn Sweet, a plant ecologist at the University of California, Riverside said in a statement. "Their numbers will decline, but how much depends on us."

加州大学河滨分校的植物生态学家、这项研究的主要作者林恩·斯威特在一份声明中说:“这些不同寻常、令人惊叹的树木的命运掌握在我们所有人的手中。它们的数量将会下降，但这在很大程度上取决于我们。”

Individual Joshua trees can live as long as 300 years. One of the ways adult trees survive so long is their camel-like ability to store large amounts of water, which helps them make it thorough the area's severe droughts.

单独的约书亚树可以活到300岁。成树存活如此之久的原因之一是它们像骆驼一样能够储存大量的水，这有助于它们彻底应对该地区的严重干旱。

However seedlings and young trees aren't able to store water this way. During long dry spells — such as the 376-week-long drought in California that lasted through March 2019 — the ground is too parched in the park to support new young plants. With climate change and rising temperatures, long droughts are expected to occur more often, which means fewer Joshua trees will likely survive into adulthood.

然而，幼苗和幼树不能以这种方式储存水分。在漫长的干旱时期——比如加州持续了376周的干旱，一直持续到2019年3月——公园里的土地太干燥了，无法种植新的幼苗。随着气候变化和气温的上升，长时间的干旱预计会更频繁地发生，这意味着成人期的约书亚树可能会更少。

But climate change isn't the only threat to these trees. They are also threatened by wildfires, which have been occurring more frequently in recent years. Fewer than 10% of Joshua trees survive wildfires.

但气候变化并不是这些树木面临的唯一威胁。它们还受到野火的威胁，近年来野火发生得越来越频繁。不到10%的约书亚树能在野火中幸存下来。

"Fires are just as much a threat to the trees as climate change, and removing grasses is a way park rangers are helping to protect the area today," Sweet said. "By protecting the trees, they're protecting a host of other native insects and animals that depend on them as well."

斯威特说:“火灾对树木的威胁不亚于气候变化。如今，公园管理员正在帮助保护这一地区。通过保护树木，他们也在保护大量其他依赖树木的本土昆虫和动物。”