Ecosystem Migration
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Ecosystem migration and evolution

Ari Shapiro recently wrote on the subject of forest migration for NPR. The article, entitled “Believe It Or Not, Forests Migrate — But Not Fast Enough For Climate Change,” was interesting and informative, but the title missed the mark. Anthropocene climate change is admittedly too rapid for forest migration to keep up. But the title is generically untrue since climate change is the driver for forests to creep across our continents as the millenniums slowly pass—forests migrate because of climate change. The shifting of forests also marks the shifting of ecosystems. An important point not elaborated on in the article is; if forests can’t keep up with climate change, then we get ecosystem evolution, and the forest transforms into a different web of life adapted to the new environmental conditions.

Shapiro’s article is about the book The Journeys of Trees by Zach St. George, where he writes: “The migration of a forest is just many trees sprouting in the same direction…. Through the fossils that ancient forests left behind, scientists can track their movement over the eons. They shuffle back and forth across continents, sometimes following the same route more than once, like migrating birds or whales.“—quite a poetic description. 

Ecosystem drift

A forest is an anchor around which an ecosystem builds, and its trees provide shelter, food, carbon/nutrient recycling, and much more. Forests adapt to the regional environmental conditions with tropical, temperate, and boreal forests thriving in their respective latitude ranges.  

But trees can’t move, and migration is a slow process requiring many generations to creep even short distances across the landscape. Current studies of ecosystem migration often focus on marine systems where tracking significant shifts over decades are possible. Entire food webs in the open ocean drift poleward as tropical waters warm. These rapid changes bring international boundary disputes when entire fisheries move from one location to the next.

The migration of forest ecosystems is sometimes augmented through human management by planting new trees in the direction of migration. But the process is fraught with uncertainties and subject to blunder. The challenge is understanding relationships between the wide range of plant and animal species that form an ecosystem. Trees are a vital part of a living system that requires a complex ecological balance for survival. The unknowns are often greater than the knowns in such complex systems.

Ecosystem evolution

This discussion begs the question: What happens if the forest can’t migrate fast enough? The harsh reality is that the existing ecosystem disappears, and a new one replaces it. The formidable and hostile Sahara desert was an oasis of green 11,000 years ago. Water was not scarce, and lakes, rivers, and wetlands covered the landscape. Trees grew, and grasslands covered what is now barren sand. But change came in a geological flash about 5000 years ago. Climatic conditions changed rapidly, and the ecosystems there didn’t migrate, they simply disappeared.

Ecosystem evolution is the threat Anthropocene climate change brings to humanity. The lifeblood of the American southwest is the Colorado River. But today, twenty years into a mega-drought, the river is running dry and can’t continue to support the vast array of water needs from cities and agriculture. As that ecosystem evolves to meet dryer and harsher environmental conditions, an entire region must question how climate change controls its future.


ArcheanWeb:

Hot and dry in the Western USA, a megadrought in progress (Source: ArcheanWeb) – https://archeanweb.com/2020/04/21/hot-and-dry-in-the-western-usa-a-megadrought-in-progress/  Also:

The Colorado River is running dry (Source: ArcheanWeb) – https://archeanweb.com/2020/03/03/the-colorado-river-is-running-dry/   Also:

Changing currents cause North Atlantic ecosystem drift (Source: ArcheanWeb) – https://archeanweb.com/2020/05/07/changing-currents-cause-north-atlantic-ecosystem-drift/  Also:


Sources:

Believe It Or Not, Forests Migrate — But Not Fast Enough For Climate Change (By Ari Shapiro; NPR) – https://www.npr.org/2020/07/28/896030567/believe-it-or-not-forests-migrate-but-not-fast-enough-for-climate-change/  Also:      

Sahara Went from Green to Desert in a Flash (By Becky Oskin; Live Science) – https://www.livescience.com/28493-when-sahara-desert-formed.html  Also:

Feature Image: Tall Trees – Source: Archeanweb

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.