How ecosystems recover following destructive volcanic lava flows

Volcanic eruptions can be one of nature’s most destructive forces with lava scorching anything in its path and disrupting the local ecosystem for thousands of years.

Lava flows from eruptions, such as the KÄ«lauea eruption in Hawaii, not only endanger lives and property, but can also destroy large swaths of trees and vegetation.

“These volcanic eruptions and things like landslides, major hurricanes, along earthquake fault lines and tsunamis just completely bury everything with entirely fresh earth, it’s a complete do-over, “ said Paul Whitefield, a natural resource specialist at Wupatki, Sunset Crater Volcano, and Walnut Canyon National Monuments in Arizona.

A lush landscape can turn into a field of jagged volcanic rock in a matter of days, having significant impacts on the local ecosystem and forcing animals out of their habitat.

Once the eruption has ended, the ecosystem begins its slow transformation as plant life gradually returns. This process is known as ecological succession.

The amount of time it takes for vegetation to return to lava flow areas is highly variable from eruption to eruption and is dependent on many different factors.

“The main variables are the prevailing climate [and] the eruption zone where it occurred,” Whitefield said.

The ecosystem will recover faster in a wetter, more tropical climate than a drier, temperate climate, Whitefield added.

Other aspects of the weather can also have an impact, such as the temperatures throughout the year and the prevailing wind direction.

“Another variable is the actual type of volcanic rock,” Whitefield said.

Some types of volcanic rock, such as andesite, are weathered down over time to become a more fertile material for plant life when compared to rock like basalt, the type of rock found at Hawaii's KÄ«lauea volcano.

This can ultimately help to speed up the process of vegetation being reintroduced naturally in an area impacted by a lava flow.

The ample rainfall along the windward slopes of the Hawaiian Islands helps the re-vegetation process, including on the Big Island of Hawaii where there have been several notable eruptions in the past 100 years.

“The [lava] flows from 1955 and 1960 have sparse ‘ohi‘a and other woody species mixed with lichens and mosses,” said Sierra McDaniel, botanist at Hawaii Volcanoes National Park.

The ‘ohi‘a is the keystone species of the Hawaiian rainforest and can range in size from a shrub to a tree more than 60 feet tall.

“The current lower east rift eruption is located in a low-elevation wet environment. Prior to the eruption, this area was a mix of native and non-native forest, farms and neighborhoods,” McDaniel said.

The colonization of the new flows will likely be similar to the lava flows of 1955 and 1960, McDaniel said.

While wooded plants are already growing on flows that are less than 70 years old, it will take much longer for plant life to become well established across the area.

In a 2013 study conducted on the origin of the Hawaiian rainforest and its transition states in long-term primary succession, D. Mueller-Dombois and H.J. Boehmer said that lower plant life-forms can begin to develop as early as one year after an eruption.

‘Ohi‘a have been observed growing as early as four years after a flow, but is takes another 200 to 400 years for the plants to mature and become well established across the area.

The long-term development of an ecosystem in an area impacted by a lava flow may take 1,000 to 25,000 years.

The ecological succession in the Hawaiian lava flow areas occurs at a much quicker pace than other volcanic eruptions in the United States, such as the Sunset Crater Volcano, located northeast of Flagstaff, Arizona.

This is one of the more recent volcanic eruptions to take place in the contiguous U.S., having last erupted approximately 900 years ago.

“We are getting tree growth, but it is still very patchy, and very tentative. It’s nothing like the typical ponderosa pine forest vegetation type [found across the region].” Whitefield said.

“It’s very very difficult for plant life to establish either on the solid rock or just the coarse material. There is just no place for a plant seed to land and germinate,” Whitefield said.

The climate at the Sunset Crater Volcano is colder and much drier than the Hawaiian Islands. This part of Arizona sees freezing temperatures every night for seven months out of the year and averages around 18 to 22 inches of precipitation, most of which falls as snow.

It has taken a long time for volcanic rock to be able to sustain well established plant life due to the arid and cold climate.

“A tree didn’t survive at least up close where the [volcanic cinder and ash] was the deepest for 450 years after the volcano went extinct, so it stayed largely barren for half the period of time from the eruption until now,” Whitefield said.

One of the fastest ecological successions on record took place in Mexico during the late 1940s with plant life returning to a flow area in just a few decades.

“There was a cinder cone volcano in central Mexico that erupted in 1947. [The eruption] completely buried their corn fields and destroyed their village and everything, and they were farming on it within 30 years and growing corn again,” Whitefield said.

One of the key factors of being able to farm on this land in such a short period of time after an eruption had to do with the climate and its proximity to Earth’s equator.

“Sea level and tropical climates have a lot more moisture. The land is very productive, very fertile and vegetation seems to recover there very quickly,” Whitefield added.

However, areas near an active volcano are always at risk of new lava flows developing.

These new flows can disrupt any progress that an ecosystem has made to reestablish itself in the region, starting the process over again.

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