patrickbdevaney/mia9 · Datasets at Hugging Face

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live oak (Quercus virginiana) and other trees with which it competes, and can itself grow as a
tree, a shrub, or a woody vine (Spector and Putz 2006), it crowds out native tree species in coastal
hammocks up to about the same latitude as where mangroves stop.
Rising sea levels have driven the inland and uphill migration of Big Bend ecosystems since
the end of the last glacial period some 14,000 years ago as they did during previous interglacials.
The current rate of rise is by no means unprecedented; sea levels were rising more than twice as
fast when paleoindians occupied the area. What is different now is that the uphill and inland
migration is often impeded by the infrastructure of humans who are less willing to move than
68 • MICHAEL I. VOLK ET AL.
our coastal predecessors. Given the low human population density and sparsity of development
along the Big Bend Coast, the financial consequences of sea level rise are modest in the aggregate
while devastating for the people who do live in the region.
Changes in Mangrove Distribution within the Florida Peninsula
Mangrove forests consisting of black mangrove, red mangrove (Rhizophora mangle), and white
mangrove (Laguncularia racemose) are a common coastal community on both the low energy
Gulf and Atlantic shorelines in Florida. Along with tidal marshes and other coastal ecosystems,
they provide a number of important services including carbon storage, shoreline protection and
sediment accretion, water quality improvement, habitat for a number of important fish and
wildlife species, as well as recreational opportunities (Osland et al. 2013).
The northern extent of each of the three mangrove species endemic to Florida varies due to
differing resilience to freeze events. Precise range boundaries are difficult to determine, but over
the past century, black and white mangroves have been found as far north as the Guana Tolomato
Matanzas National Estuarine Research Reserve on the East Coast (Wunderlin and Hansen 2008;
Zomlefer et al. 2006) and as far north as Cedar Key on the West Coast of Florida. Typically red
mangroves are found further south than the other species due to a greater sensitivity to cold
temperatures.
However, these ranges are not static, and as already noted change continues to occur. For
example, in the Ten Thousand Islands, between 1927 and 2005 mangrove encroachment occurred
upstream into salt and brackish marshes resulting in a roughly 35% increase in mangrove
coverage (Krauss et al. 2011). Within the Tampa Bay region, Raabe et al. (2012) have
documented conversion of marsh to mangrove habitat by comparing digitized nineteenth century
topographic and public land surveys with 2005 digital land cover. Though specific conversion
rates varied in different locations, the average ratio of non-mangrove to mangrove habitat over a
125-year period reversed from 86:14 to 25:75 across the four sites that they examined.
Depending on location, there are varying and interrelated reasons for these shifts that have
been cited, including construction of waterways and interruption/reduction of freshwater flows
(Krauss et al. 2011; Raabe et al. 2012), sea level rise (Krauss et al. 2011; Raabe et al. 2012), and
changes in temperature resulting from climate change (Raabe et al. 2012; Williams et al. 2014)
Storm disturbances have been a historic driver of change in forest structure (Doyle et al. 1995),
and future changes may also be driven by precipitation (Ward et al. 2016),
South to north shifts in mangrove ranges seem particularly telling of the influence of climate
change because, at least in Florida, the northern distribution of mangroves is limited by
temperature. When mangroves begin to migrate further north, it is an indication that freeze events
are no longer limiting colonization of mangroves in places where they have not recently existed.
Northern migration of mangroves along the Atlantic Coast is now being documented and
attributed to climate change. The frontline of this change is the Guana Tolomato Matanzas
National Estuarine Research Reserve. In a 2013 study, Williams et al. (2014) surveyed the
FLORIDA LAND USE AND LAND COVER CHANGE IN THE PAST 100 YEARS • 69
northernmost locations of black, red, and white mangroves, and compared those locations with
historical data identifying the northern extent of these species. In the case of black mangroves,
they found an occurrence 27 km north of the prior most northerly occurrence documented in
2007 (Wunderlin and Hansen 2008). They found a red mangrove 26 km north of the previous
outlier documented in 2006 (Zomlefer et al. 2006) and a white mangrove occurrence
approximately 67 km north of historic observations.
The overall future trend may be a gradual intrusion and northern expansion of mangroves
into areas that have historically been dominated by saltmarshes or other types of coastal habitat.
Whether this trend will continue, at what rate, and with what effect remains to be seen. At the
very least, the changes that have occurred to date underscore the importance of minimizing
human influences on these systems, including alteration of hydrology and freshwater flows. The
ultimate impacts from climate change on coastal ecosystems is uncertain, but minimizing human
impacts will help natural systems remain as resilient as possible to the changes that will occur.
Land Cover Changes in the Florida Keys
The Florida Keys are one of the most sensitive and at-risk regions in Florida with regard to
climate change, and especially sea level rise, and changes to land cover to date are already being
documented. One example is the loss of South Florida slash pine forest (Pinus elliottii var densa)
as described by Alexander (1976) and Ross et al. (1993) in the Lower Keys. In a study on Key
Largo, Alexander (1976) proposed that sea level rise was the cause of this loss, where flooded
low-lying freshwater dependent pine communities had been replaced by more salt tolerant
mangroves. A second and later study by Ross et al. (1993) reached the same conclusion through
an examination of aerial photos and field evidence to compare historic and current distribution
of pines on Sugarloaf Key. Ross et al. (1993) estimated the historical extent of pines on Sugarloaf
Key to be approximately 217 acres prior to 1935. At the time of their study in 1991, it had been
reduced to approximately 74 acres, with the earliest mortalities in areas with the lowest
elevations. The areas of early pine mortality had been populated by new salt tolerant species.
They also found that groundwater and soil water salinity were higher in areas of rapid pine forest
reduction, and that pines in those areas exhibited higher physiological stress. At the time of their
study, local sea levels had increased by 15 cm over the past 70 years, with the implication that
further sea level rise would only increase the loss of upland pine communities. Ultimately, the
entire Florida Keys as an upland ecosystem is endangered by projected sea level rise in the next
century, which will necessitate consideration of various conservation strategies including
potentially translocation of the many endangered species and subspecies found here (Noss et al.
2014).
The Impacts of Land Cover and Land Use Change on Florida’s Climate
It is important to understand that the land cover and land use changes that have occurred in
Florida have affected the climate — certainly in their contribution to the greater phenomenon of
70 • MICHAEL I. VOLK ET AL.
global climate change, but also most likely at a regional and local level. These changes in turn
affect land cover and land use in the future. As described elsewhere in this chapter, the pre-1900
landscape of Florida has been significantly altered by agriculture and urbanization. One impact
of dense urbanization can be the “heat island effect,” where urban areas actually cause an increase
in local temperatures due to the absorption and re-radiation of solar heat by buildings and paved
surfaces. Within an urban or suburban environment, local temperatures can vary based on the
amount of tree cover and density of buildings and paved surfaces. For example, a study conducted
by Sonne et al. (2000) in Melbourne, Florida showed average summer temperatures to be as
much as 1.3 degrees cooler in an undeveloped, forested site when compared to an adjacent
residential site with 4.6 houses/hectare and significant tree canopy. Average temperatures were
up to 2.9 degrees cooler when compared to a residential site without trees and 10.1
houses/hectare.
At the peninsular scale, Marshall et al. (2004) conducted a series of simulations that found
urbanization and agricultural conversion during the 20th century has contributed to a regional

live oak (Quercus virginiana) and other trees with which it competes, and can itself grow as a

tree, a shrub, or a woody vine (Spector and Putz 2006), it crowds out native tree species in coastal

hammocks up to about the same latitude as where mangroves stop.

Rising sea levels have driven the inland and uphill migration of Big Bend ecosystems since

the end of the last glacial period some 14,000 years ago as they did during previous interglacials.

The current rate of rise is by no means unprecedented; sea levels were rising more than twice as

fast when paleoindians occupied the area. What is different now is that the uphill and inland

migration is often impeded by the infrastructure of humans who are less willing to move than

68 • MICHAEL I. VOLK ET AL.

our coastal predecessors. Given the low human population density and sparsity of development

along the Big Bend Coast, the financial consequences of sea level rise are modest in the aggregate

while devastating for the people who do live in the region.

Changes in Mangrove Distribution within the Florida Peninsula

Mangrove forests consisting of black mangrove, red mangrove (Rhizophora mangle), and white

mangrove (Laguncularia racemose) are a common coastal community on both the low energy

Gulf and Atlantic shorelines in Florida. Along with tidal marshes and other coastal ecosystems,

they provide a number of important services including carbon storage, shoreline protection and

sediment accretion, water quality improvement, habitat for a number of important fish and

wildlife species, as well as recreational opportunities (Osland et al. 2013).

The northern extent of each of the three mangrove species endemic to Florida varies due to

differing resilience to freeze events. Precise range boundaries are difficult to determine, but over

the past century, black and white mangroves have been found as far north as the Guana Tolomato

Matanzas National Estuarine Research Reserve on the East Coast (Wunderlin and Hansen 2008;

Zomlefer et al. 2006) and as far north as Cedar Key on the West Coast of Florida. Typically red

mangroves are found further south than the other species due to a greater sensitivity to cold

temperatures.

However, these ranges are not static, and as already noted change continues to occur. For

example, in the Ten Thousand Islands, between 1927 and 2005 mangrove encroachment occurred

upstream into salt and brackish marshes resulting in a roughly 35% increase in mangrove

coverage (Krauss et al. 2011). Within the Tampa Bay region, Raabe et al. (2012) have

documented conversion of marsh to mangrove habitat by comparing digitized nineteenth century

topographic and public land surveys with 2005 digital land cover. Though specific conversion

rates varied in different locations, the average ratio of non-mangrove to mangrove habitat over a

125-year period reversed from 86:14 to 25:75 across the four sites that they examined.

Depending on location, there are varying and interrelated reasons for these shifts that have

been cited, including construction of waterways and interruption/reduction of freshwater flows

(Krauss et al. 2011; Raabe et al. 2012), sea level rise (Krauss et al. 2011; Raabe et al. 2012), and

changes in temperature resulting from climate change (Raabe et al. 2012; Williams et al. 2014)

Storm disturbances have been a historic driver of change in forest structure (Doyle et al. 1995),

and future changes may also be driven by precipitation (Ward et al. 2016),

South to north shifts in mangrove ranges seem particularly telling of the influence of climate

change because, at least in Florida, the northern distribution of mangroves is limited by

temperature. When mangroves begin to migrate further north, it is an indication that freeze events

are no longer limiting colonization of mangroves in places where they have not recently existed.

Northern migration of mangroves along the Atlantic Coast is now being documented and

attributed to climate change. The frontline of this change is the Guana Tolomato Matanzas

National Estuarine Research Reserve. In a 2013 study, Williams et al. (2014) surveyed the

FLORIDA LAND USE AND LAND COVER CHANGE IN THE PAST 100 YEARS • 69

northernmost locations of black, red, and white mangroves, and compared those locations with

historical data identifying the northern extent of these species. In the case of black mangroves,

they found an occurrence 27 km north of the prior most northerly occurrence documented in

2007 (Wunderlin and Hansen 2008). They found a red mangrove 26 km north of the previous

outlier documented in 2006 (Zomlefer et al. 2006) and a white mangrove occurrence

approximately 67 km north of historic observations.

The overall future trend may be a gradual intrusion and northern expansion of mangroves

into areas that have historically been dominated by saltmarshes or other types of coastal habitat.

Whether this trend will continue, at what rate, and with what effect remains to be seen. At the

very least, the changes that have occurred to date underscore the importance of minimizing

human influences on these systems, including alteration of hydrology and freshwater flows. The

ultimate impacts from climate change on coastal ecosystems is uncertain, but minimizing human

impacts will help natural systems remain as resilient as possible to the changes that will occur.

Land Cover Changes in the Florida Keys

The Florida Keys are one of the most sensitive and at-risk regions in Florida with regard to

climate change, and especially sea level rise, and changes to land cover to date are already being

documented. One example is the loss of South Florida slash pine forest (Pinus elliottii var densa)

as described by Alexander (1976) and Ross et al. (1993) in the Lower Keys. In a study on Key

Largo, Alexander (1976) proposed that sea level rise was the cause of this loss, where flooded

low-lying freshwater dependent pine communities had been replaced by more salt tolerant

mangroves. A second and later study by Ross et al. (1993) reached the same conclusion through

an examination of aerial photos and field evidence to compare historic and current distribution

of pines on Sugarloaf Key. Ross et al. (1993) estimated the historical extent of pines on Sugarloaf

Key to be approximately 217 acres prior to 1935. At the time of their study in 1991, it had been

reduced to approximately 74 acres, with the earliest mortalities in areas with the lowest

elevations. The areas of early pine mortality had been populated by new salt tolerant species.

They also found that groundwater and soil water salinity were higher in areas of rapid pine forest

reduction, and that pines in those areas exhibited higher physiological stress. At the time of their

study, local sea levels had increased by 15 cm over the past 70 years, with the implication that

further sea level rise would only increase the loss of upland pine communities. Ultimately, the

entire Florida Keys as an upland ecosystem is endangered by projected sea level rise in the next

century, which will necessitate consideration of various conservation strategies including

potentially translocation of the many endangered species and subspecies found here (Noss et al.

2014).

The Impacts of Land Cover and Land Use Change on Florida’s Climate

It is important to understand that the land cover and land use changes that have occurred in

Florida have affected the climate — certainly in their contribution to the greater phenomenon of

70 • MICHAEL I. VOLK ET AL.

global climate change, but also most likely at a regional and local level. These changes in turn

affect land cover and land use in the future. As described elsewhere in this chapter, the pre-1900

landscape of Florida has been significantly altered by agriculture and urbanization. One impact

of dense urbanization can be the “heat island effect,” where urban areas actually cause an increase

in local temperatures due to the absorption and re-radiation of solar heat by buildings and paved

surfaces. Within an urban or suburban environment, local temperatures can vary based on the

amount of tree cover and density of buildings and paved surfaces. For example, a study conducted

by Sonne et al. (2000) in Melbourne, Florida showed average summer temperatures to be as

much as 1.3 degrees cooler in an undeveloped, forested site when compared to an adjacent

residential site with 4.6 houses/hectare and significant tree canopy. Average temperatures were

up to 2.9 degrees cooler when compared to a residential site without trees and 10.1

houses/hectare.

At the peninsular scale, Marshall et al. (2004) conducted a series of simulations that found

urbanization and agricultural conversion during the 20th century has contributed to a regional