With few hard frosts, tropical mangroves push north

With few hard frosts, tropical mangroves push north
A newly established black mangrove grows amid salt marsh plants north of St. Augustine, Florida, near the northern limit of this cold-sensitive tropical tree's range. Mangroves are expanding into North Florida as killing frosts become rare there. Credit: Kyle C. Cavanaugh

Cold-sensitive mangrove forests have expanded dramatically along Florida's Atlantic Coast as the frequency of killing frosts has declined, according to a new study based on 28 years of satellite data from the University of Maryland and the Smithsonian Environmental Research Center in Edgewater, Maryland.

Between 1984 and 2011, the Florida Atlantic coast from the Miami area northward gained more than 3,000 acres (1,240 hectares) of mangroves. All the increase occurred north of Palm Beach County. Between Cape Canaveral National Seashore and Saint Augustine, mangroves doubled in area. Meanwhile between the study's first five years and its last five years, nearby Daytona Beach recorded 1.4 fewer days per year when temperatures fell below 28.4 degrees Fahrenheit (-4 degrees Celsius). The number of killing frosts in southern Florida was unchanged.

The mangroves' march up the coast as far north as St. Augustine, Florida is a striking example of one way 's impacts show up in nature. Rising temperatures lead to new patterns of extreme weather, which in turn cause major changes in plant communities, say the study's authors.

Unlike many studies which focus on changes in average temperatures, this study, published online Dec. 30 in the peer-reviewed journal Proceedings of the National Academy of Sciences, shows that changes in the frequency of rare, severe events can determine whether landscapes hold their ground or are transformed by climate change.

The are edging out , said University of Maryland Entomology Prof. Daniel S. Gruner, a study co-author. "This is what we would expect to see happening with climate change, one ecosystem replacing another," said Gruner, who co-leads an interdisciplinary research project on mangrove ecosystems, along with Ilka C. Feller of the Smithsonian. "But at this point we don't have enough information to predict what the long term consequences will be."

One valuable ecosystem replaces another – at what cost?

"Some people may say this is a good thing, because of the tremendous threats that mangroves face," said the study's lead author, Kyle Cavanaugh, a Smithsonian postdoctoral research fellow. "But this is not taking place in a vacuum. The mangroves are replacing salt marshes, which have important ecosystem functions and food webs of their own."

Mangrove forests grow in calm, shallow coastal waters throughout the tropics. Salt marshes fill that niche in temperate zones. Both provide crucial habitat for wildlife, including endangered species and commercially valuable fish and shellfish. Some animals use both types of habitat. Others, like marsh-nesting seaside sparrows or the honey bees that produce mangrove honey, rely on one or the other.

Both provide valuable ecosystem services, buffering floods, storing atmospheric carbon and building soils. Both are in decline nationally and globally. Mangrove forests are cut down for charcoal production, aquaculture and urbanization or lose habitat to drainage projects. Salt marshes are threatened by drainage, polluted runoff and rising sea levels.

Florida naturalists noticed that mangroves now grow in places that once were too chilly for the tropical trees. "We knew this was happening, but no one knew if it was a local or a regional phenomenon," Cavanaugh said.

Study used satellite photos, the "gold standard" in climate change

Cavanaugh, an expert in remote sensing, turned to photographs of Florida's Atlantic coast taken by Landsat 5, a satellite launched by NASA and the USGS in 1984 to track changes in Earth's land cover. Landsat 5 kept working until 2011. "It very quickly became a gold standard to examine the effects of climate change, because it lets you look back in time," Cavanaugh said.

The satellite images revealed the mangroves' expansion into terrain formerly inhabited by salt marsh plants. While the study only looked at the Atlantic Coast, the same trend is taking place on Florida's Gulf Coast, Cavanaugh and Gruner said.

Mean winter temperatures have risen at seven of eight coastal weather stations in the study area. But if overall warming benefited mangroves, the mangrove cover should have increased all over Florida, not only in the north. Average winter temperature, rainfall, and urban or agricultural land use did not explain the mangroves' expansion. Only fewer freezing days at the northern end of their range matched the trend.

The researchers are studying effects on coastal insects and birds; whether the change will affect coastal ecosystems' ability to store carbon; and whether juvenile fish and commercially valuable shellfish will remain abundant in the changing plant communities.

Cavanaugh is looking at Landsat 5 imagery for Mexico, Peru, Brazil, Australia and New Zealand to see if are expanding elsewhere as they are in Florida.

Explore further

Better protection for mangroves with models for successful seedling establishment

More information: "Poleward expansion of mangroves is a threshold response to decreased frequency of extreme cold events," published online Dec. 30, 2013 in Proceedings of the National Academy of Sciences. www.pnas.org/cgi/doi/10.1073/pnas.1315800111
Citation: With few hard frosts, tropical mangroves push north (2013, December 30) retrieved 14 October 2019 from https://phys.org/news/2013-12-hard-frosts-tropical-mangroves-north.html
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Dec 30, 2013
Who forgot to tell these trees climate change is a myth??? Somebody on the right slipped up on that one, and I bet they're gonna pay.

Dec 30, 2013
"Who forgot to tell these trees climate change is a myth??? Somebody on the right slipped up on that one, and I bet they're gonna pay."

Clearly these scientists... like all others who study things which might be affected by changes in global climate, are part of a mass conspiracy to sully fossil fuel companies reputations... thank god for unbiased media like fox news and the daily mail coming to the rescue... cough cough.

Dec 30, 2013
When hard frosts return, mangroves will die.

Vikings farmed Greenland for over 200 years.

Dec 30, 2013
This is pathetic. First they're blaming global warming on a coastal phenomena, then admit freezes south of these regions are unchanged. Obviously, the difference here is a matter of prevailing wind direction (onshore v. offshore), which may, or may not have anything to do with global warming.

And they don't even bother to consider seed transport!

And lastly, major freezes in Florida are historiclly extremely sporadic.


Dec 31, 2013
It's no use...the followers of the alarmist religion have no need for science. As we know, no one seriously denies climate change. It's been happening for 4.5 billion years, but the followers of this religion simply have to self flagellate in public.
The science, and the article says that there has been so difference in frosts. OTOH it does continue the lie about extreme weather. Funny that hurricanes and tornadoes are at historic lows with no trend on droughts or floods. So, where is the extreme weather?
I'd say that if the result of adding more CO2 to the atmosphere is what we are observing, specifically less extreme weather and the expansion of habitat, then by all means, lets' burn more carbon.

Dec 31, 2013
Who forgot to tell these trees climate change is a myth??? Somebody on the right slipped up on that one, and I bet they're gonna pay.

Who tells you that the trees aren't genetically modified with alien DNA and planted by the Evil Minons of IPCC in a Global Conspiracy(TM) against the US taxpayer?

Dec 31, 2013
When hard frosts return, mangroves will die.

Vikings farmed Greenland for over 200 years.

yes and they would have been able to do it after the "little ice age" too. Stange, you guys are always giving a religious tint to the term "Little Ice Age" but now it happens that it's just the explanation against your argument that "the climate was warmer in the past". Nope, it wasn't warmer: It was 'normal'and it grew colder for some time, enough to srew up the poor vikings.

Source: http://en.wikiped...reenland

Yes, it's just Wikipedia, but at least it's not me saying "believe this because I'm extremely cool"

And beware of the Evil IPCC Minions, they are everywhere abducting people to work in their smoked salmon mines in Siberia!!!

Dec 31, 2013
Beware the longer cycles and the lethal affects of longer cycle short term climate extremes for invalidating this kind of study. Being an old Florida marine biologist, I would have to say the studies validity is limited by the short term history of satellite photos. Had they been available for the previous decade (early 70s) they would have shone the complete collapse of the longer cycle mangrove colonization advances - when we had a week of low 20s as far south as the Keys - snowing in the Bahamas and killing some mangroves even there. Very unfortunate for me - a student doing studies on non-indigenous tropical fish populations. The study isn't completely meaningless, but a data point with very limited term for making global climate change proclamations. Let's revisit the study in 200 yrs. and see if there is a trend or a cycle at work with regard to mangroves moving north. Meanwhile let's continue to ignore the primary cause of CO2 & all anthropogenic impacts - human overpopulation.

This is another example of a conservation success story hijacked to create an illusion of climate catastrophe. The authors completely ignore the fact that because mangroves had been threatened from coastal development and changes in the hydrology there has been coordinated efforts to restore mangroves. Nurseries were created and plantings have been carried out in the very area where the increased population of mangroves were purportedly only explained by climate change. This is shameless science.

Jan 01, 2014
Good God.
Even the Australian Bureau of Meteology is shamelessly offering their opinions for filthy lucer.
Is there no end to the conspiracies?
Has the illuminati infiltrated all?
Have the (The name elludes me) aliens who live in underground cities and are bent on having their wicked way with women and cows, won?

Jan 01, 2014
Palm trees will look lovely on Cape Cod! :)

Jan 02, 2014
"The polar bears are drowning" - algore, progressive leftist socialist whatever he needs to be, inventor of the Internet

"The polar bears will be fine." - Freeman Dyson, Inst. of Advanced Studies, Spock level genius.

Who you gonna believe?

Jan 05, 2014
" JACKSONVILLE, Fla. -- A snowy owl has made a rare appearance in Florida.

The Florida Times-Union reports (http://bit.ly/1atwPrP ) that one of the Arctic birds has been spotted since last week in Little Talbot Island State Park. It's only the third-ever sighting of a snowy owl confirmed in Florida.

Park services specialist Peter Maholland says bird watchers have been flocking to northeast Florida to catch a glimpse of the white bird.

Read more here: http://www.miamih...link=cpy

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