Forests, range land and the fire risk

Drought can also have longer-term impacts on ecosystems, particularly forest health.

The Sierra Nevada range has seen large-scale tree die-offs with the drought in recent years, including in northern areas around Lake Tahoe and Reno that weren’t as affected by the previous drought. Whether the recent die-offs there are due to the severity of the current drought or lingering effects from the past droughts is an open question.

Even with a wet winter, it’s not clear how soon the forests will recover.

Rangelands, since they are mostly grasses, can recover in a few months. The soil moisture is really high in a lot of these areas, so range conditions should be good across the West — at least going into summer.

If the West has another really hot, dry summer, however, the drought could ramp up again, particularly in the Northwest and California. And then communities will have to think about fire risk.

Right now, there’s a below-normal likelihood of big fires in the Southwest for early spring due to lots of soil moisture and snowpack.

In the higher-elevation mountains and forests, the above-average snowpack is likely to last longer than it has in recent years, so those regions will likely have a later start to the fire season. But lower elevations, like the Great Basin’s shrub- and grassland-dominated ecosystem, could see fire danger starting earlier in the year if the land dries out.

Arizona and New Mexico, the opposite happened.

Seasonal forecasts tend to rely heavily on whether it’s an El Niño or La Niña year, involving sea surface temperatures in the tropical Pacific that can affect the jet stream and atmospheric conditions around the world. During La Niña — the pattern we saw from 2020 until March 2023 — the Southwest tends to be drier and the Pacific Northwest wetter.

But that pattern doesn’t always set up in exactly the same way and in the same place, as we saw this year.

There is a lot more going on in the atmosphere and the oceans on a shortterm scale that can dominate the La Niña pattern. This year’s series of atmospheric rivers has been one example.

Dan Mcevoy is an associate research professor in climatology at the Desert Research Institute.

This article is republished from The Conversation under a Creative Commons license.