New research from the University of California Riverside shows that Joshua trees are threatened with extinction without dramatic action to reduce climate change.
The study ran simulations based on high, moderate and low levels of climate change mitigation to understand how humans can work to protect the trees. They found that the highest level of mitigation would conserve approximately 19% of the trees’ viable habitat in Joshua Tree National Park by 2070. However, without any reduction in carbon emissions, the park would only retain about 0.02% of the trees’ habitat.
Study lead author Lynn Sweet told Phys.org that the fate of the trees is in the hands of humans. Though their numbers will decline, how many trees are able to survive climate change depends on how much people can decrease carbon emissions.
The research team solicited the help of volunteers to gather data about more than 4,000 Joshua trees to verify that climate change is already affecting the trees. They found that the trees are migrating to higher elevation parts of the park with cooler weather and more ground moisture.
Adult trees can store large reserves of water to survive long droughts – like the recent 376-week drought in California – but the younger trees and seedlings aren’t capable of holding water in this way. As climate change increases the chances of droughts, these young trees aren’t able to grow.