除非我們應對氣候變化，否則約書亞樹將在2070年面臨滅絕

除非我們應對氣候變化，否則約書亞樹將在2070年面臨滅絕

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

外表引人注目的約書亞樹自更新世以來存活了大約250萬年?，F(xiàn)在，由于氣候變化，它們的滅絕迫在眉睫。

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.

在一項新的研究中，研究人員和一組志愿者收集了南加州約書亞樹國家公園4000多棵樹的數(shù)據(jù)。他們發(fā)現(xiàn)，這些樹木已經(jīng)遷移到公園中海拔較高的地區(qū)，那里的天氣更涼爽，地面濕度更大，是樹木的安全地帶。在更干燥、更炎熱的地區(qū)，成樹不能生長出那么多的幼樹，那些生長出來的也不能存活。

Photo: Esther Lee/Flickr

Their findings were published in the journal Ecosphere.

他們的發(fā)現(xiàn)發(fā)表在《生態(tài)圈》雜志上。

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.

考慮到氣候變化的預測影響，研究人員估計了這些安全區(qū)(或“避難所”)中有多少能夠生存下來。他們預測，在最理想的情況下，如果采取重大措施降低碳排放，大約19%的樹木將在2070年后保留下來。

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，如果事情繼續(xù)這樣下去，沒有任何減少碳排放的嘗試，氣溫繼續(xù)上升，那么只有0.02%的樹木會保留下來。

"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."

加州大學河濱分校的植物生態(tài)學家、這項研究的主要作者林恩·斯威特在一份聲明中說:“這些不同尋常、令人驚嘆的樹木的命運掌握在我們所有人的手中。它們的數(shù)量將會下降，但這在很大程度上取決于我們。”

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.

單獨的約書亞樹可以活到300歲。成樹存活如此之久的原因之一是它們像駱駝一樣能夠儲存大量的水，這有助于它們徹底應對該地區(qū)的嚴重干旱。

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，幼苗和幼樹不能以這種方式儲存水分。在漫長的干旱時期——比如加州持續(xù)了376周的干旱，一直持續(xù)到2019年3月——公園里的土地太干燥了，無法種植新的幼苗。隨著氣候變化和氣溫的上升，長時間的干旱預計會更頻繁地發(fā)生，這意味著成人期的約書亞樹可能會更少。

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.

但氣候變化并不是這些樹木面臨的唯一威脅。它們還受到野火的威脅，近年來野火發(fā)生得越來越頻繁。不到10%的約書亞樹能在野火中幸存下來。

"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."

斯威特說:“火災對樹木的威脅不亞于氣候變化。如今，公園管理員正在幫助保護這一地區(qū)。通過保護樹木，他們也在保護大量其他依賴樹木的本土昆蟲和動物。”