|
Items in cart [0] |
Questions? Call 888-624-8373 |
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 145
7
Validating Prehistoric and Current
Social Phenomena upon the Landscape of the
Peten, Guatemala
Thomas L. Sever
Remotely sensed data from airborne and satellite sensors have been used to
identify archeological features, such as roadways, temples, cisterns, and agricul-
tural areas. This information is critical in research on the Maya to help answer
questions regarding subsistence, settlement patterns, population densities, soci-
etal structure, communication, and transportation. These issues in turn may well
relate to perhaps the most intriguing question of all: the reason for the Mayan
collapse.
From the perspective of space we can also view the effects of human activity
upon the landscape. Satellite images of the Peten region of Guatemala allow us
to see where, when, and how rapidly that landscape is changing. Satellite data
can be used to provide quantifiable evidence for depletion rates and trends of
deforestation, identify potential points of conflict, and create predictive models
for the future. The data can also be combined with ground-truth information to
help us better understand the social issues involved and develop an effective
strategy for balancing the challenges of population increase, sustainability, and
conservation.
Because of unanticipated preliminary results, this project evolved from a
small-scale study to a regional analysis. Originally, the project was to conduct an
archeological and environmental analysis of a 1 x 1 degree study area along the
Usumacinta river valley between Guatemala and Mexico. This work was to be
performed in response to potential hydroelectrical projects and large-scale oil
explorations that threatened the area. When the first Landsat Thematic Mapper
(TM) imagery of the area was processed, it revealed the contrast between the
tilled landscape of Mexico and the standing rainforest of Guatemala (Plate 7-1,
145
OCR for page 146
146
Mexico
100
VALIDATING SOCIAL PHENOMENA, PEIEN, GUATEMALA
Guatemala
am_
,,~
~_/ =
Scale
Belize
FIGURE 7-1 Location of the Maya Biosphere Reserve and buffer zone in the Peten
district of northern Guatemala.
after page 150~. This image received national and international attention with its
appearance in the October 1989 issue of National Geographic magazine. It was
also taken before the Guatemala Congress by President Vinicio Cerezo, which
resulted in the establishment and protection of the Maya Biosphere Reserve (MBR)
in 1990. This image also led to an agreement between the National Aeronautics and
Space Administration (NASA) and the Central American Commission on Environ-
ment and Development (CCAD) to conduct joint research as part of the Mission to
Planet Earth Program. As a result of these developments, the original study area was
expanded to include both the Peten region of Northern Guatemala and the MBR, the
protected area within the Peten's boundaries (see Figure 7-1~.
Initially, the primary focus of this investigation was on the use of remote
sensing technology for the identification of unrecorded archeological features.
However, the utility of the remote sensing data for monitoring of current defores-
tation activities was also apparent to conservationists, scientists, managers, and
OCR for page 147
THOMAS L. SEVER
147
politicians. Consequently, two avenues of research archeological inventory
and deforestation have proceeded in parallel throughout the course of the
project. These two areas of research are discussed separately here, although both
are related to the social sciences.
Using airborne and satellite remote sensing data, the project has identified
prehistoric archeological features, such as roadways, temples, and agricultural
areas, as well as documented a time-lapse sequence of deforestation from 1986 to
the present (Seder et al., 19961. The clearing of tropical forests is one of the
primary global environmental issues. Deforestation leads to three unintended
impacts: loss of cultural diversity, loss of biodiversity, and loss of carbon storage
capacity. Satellite imagery has proven to be one of the best techniques for
monitoring forest clearing, shifting cultivation, and land-use conversion patterns
(Seder, 1995; Sader et al., 1994~. While remotely sensed data provide quantifi-
able information about forest and land-cover changes, they do not explain the
anthropogenic causes for those changes. Hence ground-truth information is re-
quired both to validate the satellite imagery and to supplement it with information
from local harvesters, farmers, and ranchers regarding the criteria they employ
for land-use conversion.
Our research team consists of James Nations, an anthropologist and ecologist
at Conservation International; Santiago Billy, a Guatemalan national and conser-
vationist for Conservation International; Frank Miller, a forester at Mississippi
State University; Daniel Lee, a geographic information system (GIS) expert at
GeoTek; and the author, a remote sensing specialist and archeologist at NASA.
This interdisciplinary team has been conducting field research in the Peten for 10
years to verify the results of our computer analysis. The primary focus of our
research is environmental inventory and the detection of archeological features
within the Peten. During the course of our work we have collaborated with many
other researchers, particularly Steven Sader, University of Maine, in deforesta-
tion studies and Patrick Culbert, University of Arizona, in archeological research.
BACKGROUND
The Peten, in northern Guatemala, covers 36,000 km2 a third of
Guatemala's land mass. The wetlands and intact tropical forest of the Peten
represent one of the world's richest areas of biological diversity. The ecosystem
contains over 800 species of trees; 500 species of birds; and large populations of
mammals, including monkeys, jaguars, and tapirs. The area also contains some of
the most prehistorically significant Mayan archeological sites in Latin America.
Since deforestation activities also include the destruction of archeological sites,
conservation of these ruins is synonymous with forest protection. Only a few
indigenous Mayan descendants still live in the Peten, although the population of
inhabitants is increasing rapidly as a result of migration and settlement. Until
1970, nearly 90 percent of the Peten remained forested. Today over half of the
OCR for page 148
48
VALIDATING SOCIAL PHENOMENA, PRIER, GUATEMALA
forest has been cut, and if deforestation continues at its present rate, only 2
percent of the Peten's forest will remain by the year 2010 (Cameo, 1996~.
The MBR lies within the Peten and covers 1.6 million hectares (ha), nearly
40 percent of the Peten and 14 percent of Guatemala. It is the largest protected
area in of the Maya Tropical Forest, which stretches from Eastern Mexico to
Belize, and as such is critical to regional conservation efforts. Deforestation rates
in the area are accelerating as a result of increasing human migration. Over the
past 20 years, the human population in the Peten has increased from 20,000 to
more than 300,000 (Stuart, 1991~. Today, the Peten has a human population
density of 26 inhabitants per square mile (J. Nations, personal communication);
this figure contrasts significantly with the ancient Mayan population densities of
2,600 persons per square mile in the center and 500-1,300 per square mile in the
more rural areas (Rice, 1991).
New roads and pipelines being constructed in the Peten by logging and
petroleum companies serve as conduits for human migration (Plate 7-2, after
page 150~. Peasant farmers follow these corridors to clear the forest and establish
maize-based agricultural plots (milpas). Slash-and-burn cultivation remains the
predominant agricultural system in the Peten today. Soil fertility declines after 2
or 3 years of cultivation, and the milpas are abandoned (Lundell, 1937) as the
farmers move to new areas. In addition, a major expansion of the Q'eqchi' Maya
population has occurred in the southern Peten. The Q'eqchi', numbering over
400,000, show remarkable abilities in adapting to new environments and learning
new technologies (Cahuec and Richards, 1994~. Cattle pastures are becoming
increasingly present in the Peten, although they are not yet dominant as in other
regions of Central America.
The ancient Maya far outgrew the carrying capacity of slash-and-burn agri-
culture, which is only 200-250 persons per square mile in this region (Rice,
1991~. The environmental effects of the current deforestation and settlement in
the area are not known at this time. What is known is that monocultivation and
cattle ranching are replacing the traditional adaptive system of the past. The
forests of the Peten were nearly destroyed 1000 years ago by the ancient Maya,
who, after centuries of successful adaptation, had finally overused their resources.
Current inhabitants are threatening to do the same thing today in a shorter time
period with a lesser population.
ARCHEOLOGICAL RESEARCH
The Classic Mayan period of the southern lowlands lasted from 250 to 900
A.D., when it collapsed in unparalleled fashion. That some disaster had befallen
the Classic Maya became clear in the early days of Mayan studies when it was
learned that the dating and inscription of monuments had ceased during the ninth
century. The seventh and eighth centuries were a golden age for the Maya. A
population of millions achieved new peaks in construction. Stone monuments
OCR for page 149
THOMAS L. SEVER
149
proclaimed the glory of the rulers in decorative masterpieces. Between 830 and
930 A.D., however, populations of both elites and commoners in the Mayan
lowlands declined by two-thirds. By the Postclassic Period (after 930 A.D.), only
a few scattered houses remained (Culbert, 1993~.
The Mayan collapse may well be the greatest demographic disaster in human
history. It occurred in the region of the Mayan lowlands. There was no exodus
outward because the peripheral populations remained stable. What caused this
disaster is not known. Potential explanations include internal conflict and war-
fare, disease, climatic change, overpopulation, outside invasion, peasant rebel-
lion, soil nutrient depletion, and failure of the agricultural system (Culbert, 1974,
1993; Hammond, 1990~. Rather than having a single explanation, however, the
cataclysm may have had multiple causes. What is known is that most of the trees
in the region had been cut down by the ninth century. Although there is recent
evidence for a drought beginning around 800 A.D. (Sabloff, 1995; Curtis et al.,
1996), the question emerges of why the Maya had survived previous droughts,
not to mention other setbacks. Understanding how the Maya managed the land-
scape so successfully for centuries and what the eventual effect was, if any, of
their deforestation activities may provide an important lesson for the future of
today's inhabitants.
TM imagery reveals Mayan causeways that often cannot be seen from ground
level. As part of the theoretical framework of landscape archeology, roadways
reflect the interplay among technology, environment, social structure, and the
values of a culture (Trombold, l991~. In this case, the causeways are the tangible
evidence of the Maya's structural organization across geographic space. The
Mayan causeways are formal routes. Formal routes reflect elements of planning
and purposeful construction, including labor in construction, engineering, main-
tenance, and an organizational structure that oversees the system. They tend to be
straight in nature and are engineered to overcome natural obstacles in order to
improve transportation and communication. They contrast with informal routes,
such as paths, which show little if any evidence of construction, are irregular in
design, and tend to avoid natural obstacles. From a remote sensing perspective,
the Mayan roadways tell us how the cities were connected and to some degree
suggest the level of sophistication of the city responsible for their construction
and maintenance.
Several analytical techniques have been employed to identify Mayan cause-
ways in the TM imagery. Laplacian and Gaussian filtering techniques were used
to isolate linear and curvilinear features in the imagery. These techniques have
been employed successfully to detect Anasazi roads in New Mexico (Sever,
1990) and prehistoric footpaths in Costa Rica (Sheets and Sever, 1988~. In
addition, a number of different ratios and other transformations, such as the
Normalized Difference Vegetation Index (NDVI), principal component analysis,
and a modified version of the Kauth-Thomas (KT) transformation (MKT) were
used to isolate the causeway features. MKT was derived as follows:
OCR for page 150
150
VALIDATING SOCIAL PHENOMENA, PETEN, GUATEMALA
.
The KT tasseled cap transformation was performed using standard coeffi
cients.
· Bands 1 and 2 of the KT transformation were ratioed using Band 1 -
(Band 2/Band 1 + Band 2~. In this format, the central processing unit (CPU)
order of operations is to perform the division first and then subtract, yielding a
different value from that of the NDVI calculation. These values are assigned to
the red video color gun.
· Bands 4 and 5 were ratioed as 5/4 and assigned to the green video gun.
· Bands 5 and 7 were ratioed as 5/7 and assigned to the blue video gun.
The combination of these techniques made it possible to identify various
roadway segments. For instance, as the roads cross the seasonally flooded
swamps (bajos), they support a more lush vegetation than the surrounding plant
community. Since the TM data are collected near the end of the dry season
(April-May), the dryness of the roads in the elevated areas can be detected, as can
the wetness in some of the lower areas. The most distinguishing characteristic,
however, is the straightness or linearity of these features. The karst topography
of the landscape also reveals linear geologic faults, fractures, and drainages that
can be confused with causeways. Ground-truth reconnaissance can often resolve
this issue visually. In some cases, a ground survey is not sufficient, and excava-
tion must be used to distinguish the features conclusively. It should be mentioned
that some of the techniques used to identify roadways also reveal temple struc-
tures and man-made water storage areas (see Figure 7-2~. The 30-m resolution of
the satellite imagery precludes detection of canals, but airborne 5-m Thermal
Infrared Multispectral Scanner (TIMS) and Calibrated Airborne Multispectral
Scanner (CAMS) data, as well as simultaneously acquired color infrared (CIR)
photographs, have been used to identify potential canals and field systems. A1-
though these features have not been verified to date, their existence is supported
by the discovery of canal features in nearby study areas. The problem is that the
5-m data were not acquired in the specific bajo areas where the canals were
discovered through excavation. As discussed below, the detection of these canals
will provide insight into the use of the bajos by the Maya. The CIR photography
was also used to confirm Mayan causeways (Figure 7-3~.
One of the leading debates in Mayan archeology concerns whether the low-
land wetlands (bajos) of the Peten were or could be used for agriculture (Pope and
Dahlin, 1989, 1993; Adams et al., 1990; Turner, 1993~. The bajos represent 40
percent of the land surface of the Peten, and it seems reasonable to assume that
these areas were farmed by the ancient Maya. As noted earlier, slash-and-burn
technology, still used by the inhabitants today, can support only 200-250 persons
per square mile in the region. This level had been reached by the Maya by 300
A.D., far before their population peak in the Late Classic period (600-830 A.D.),
when population densities ranged from 500 to 2,600 persons per square mile
(Rice, 1991~.
OCR for page 151
THOMAS L. SEVER
151
FIGURE 7-2 Thematic Mapper satellite image created by ratioing Band 4 with Band 3.
The light spots represent ancient Mayan temple structures beneath the forest canopy at the
archeological site of Mirador, while the dark lines represent Mayan causeways and natu-
ral geological features. Ground reconnaissance and sometimes excavation are required to
separate the cultural from the natural features.
Currently, our research team has joined forces with Patrick Culbert of the
University of Arizona to address this issue. Both supervised and unsupervised
classification techniques (Kelley, 1983) have been used to classify satellite im-
ages and identify the bajo areas (Plate 7-3, on facing page). Three different types
of bajos have been identified, in addition to seven additional land-cover classes,
such as high forest, transition forest, and water. Local informants in the Peten,
however, have identified to Culbert seven different types of bajos, each with
OCR for page 152
152
;^
Ct
Ct =
.
Ct
o
o
~ .=
.=
Cal
s°-
;^
Cal
so
o
Cal
·_.
~ .~
. _ Cal
o ~
~ _.
~ o
Or, _.
.=
o A,
.
~ Cal
Ct Cal
·0
Hi_ Ct
sly
sol
.0 o
o ~
o
o
Cal
Cd sly
Or, L
Cal
=. ~
~ Ct
sly 5
o
o ~
·_.
o
Cal
;^
Ct
· _.
o
;^
Cal ~
Ct o
OCR for page 153
THOMAS L. SEVER
153
distinctive characteristics. Of these seven types, two or three remain sufficiently
moist in the dry season to sustain agriculture. This information is pertinent today,
and may provide insight into early Mayan farming practices. Currently, we are
applying supervised classification techniques using information from two
transects as the training samples. The transect data come from field data col-
lected by Culbert and his research team during their May 1995 field season. They
conducted two transects in the Bajo la Justa, Peten one a trail of approximately
7 km, the other along a road of approximately 17 km. They were assisted in the
vegetation survey by a native (Don Felipe Lanza) employed by the Forestry
Division of the Tikal National Park.
During this field reconnaissance they learned that there are two primary
classifications of bajo associations: palm and scrub. Within each of these two
major types are "sections characterized by a predominance of particular species
which provide subtypes such as 'escobal', 'coronal', and 'botonal' within the
palm bajo, and 'jimbal', 'tintal', 'navajuelal' and 'huechal' within the scrub bajo"
(Culbert et al., 1995:3~. Additionally, there are three distinctions that relate to
ground-surface characteristics and inundation: "bajo piano," which has a flat
surface and no noticeable slope; "bajo borbolal," which has an undulating sur-
face; and "bajo inundable," which is at an elevation where seasonal flooding
occurs and seems to be characterized by scrub vegetation. Lanza also informed
Culbert and his team that palm bajo is excellent for milpa and is one of the
environments of choice among native Peteneros. Along both transects the team
recorded vegetation according to Lanza's classification and gathered Global Po-
sitioning System (GPS) readings.
This ground-truth information has been overlaid on the TM satellite data,
and various classifications have been developed. In addition, we will acquire
standard-beam (30-m) Radarsat C-band Synthetic Aperture Radar (SAR) data,
which will then be merged with the TM data. This merging of TM/SAR data
should provide the best opportunity for distinguishing class types. The various
classification schemes will be tested during the 1998 field season to determine
which technique is the most accurate.
In the process of searching for the best satellite band combinations, ratios,
and other transformations for discriminating sacbes and bajos, it was noted that
these techniques also discriminated elevated "islands" of upland within the bajos.
The best technique for discriminating such islands employed the MKT using TM
bands 3, 4, and 5. Culbert's 1995 field season led to key findings with regard to
these islands:
A very important fact about the location of Maya sites in relation to bajos has
become clear...our work suggests that there was occupation on almost every
area of slightly higher land where patches of high forests occur as "islands"
within bajo. We call these areas of occupation "bajo communities" and they
will be one of the foci of our future project in the Bajo la Justa (Culbert et al.,
1995:4~.
OCR for page 154
154
VALIDATING SOCIAL PHENOMENA, PETEN, GUATEMALA
The discovery of these occupied islands within the bajo system raises many
research questions related to chronology, settlement patterns, and artifactual as-
semblages. Do these islands represent a long-term occupation, or are they the
result of a sudden, brief occupation? Are the bajo communities similar to or
different from other communities, and do they operate under a similar or different
organizational structure? The answers to these questions are critical in under-
standing the full adaptation of the Maya to their rainforest environment, and
mapping these islands is the first step toward finding these answers.
Recently, our research team participated in the identification of an unre-
corded site that may prove to be Site Q (for ''que?''L''which?''l). The potential
existence of this Mayan site has been based on relief sculptures found in various
collections and museums, as first identified by Peter Mathews in the late 1970s.
The location of Site Q. signified by a snake-head emblem glyph, has been a
source of debate among scholars, with some postulating that the site has not yet
been found and others claiming that it is the known site Calakmul in Mexico
(Schuster, 1997~. The preeminence of Site Q in the Classic Maya world is
evidenced by the fact that the snake-head emblem glyph has been found in
inscriptions at sites in Belize, Guatemala, Honduras, and Mexico. While
Calakmul is a strong candidate for Site Q. the fact remains that there are a number
of large Mayan sites in the area where little or no research has been conducted,
not to mention potential sites that have not yet been found.
While studying scarlet macaw routes, team member Santiago Billy came
across an unrecorded site in April 1996. His GPS measurements of this location
were compared with TM satellite imagery in which potential causeway linea-
ments could be seen by the author. Our team conducted an initial reconnaissance
mission in July 1996. Pyramids, walls, plazas, structures, and hieroglyphic monu-
ments could be seen. The research team reported this information to Ian Graham
and David Stuart at the Harvard Peabody Museum.
In May 1997, our research team met Graham and Stuart at the site, which has
been named "La Carona." As they mapped the site and recorded the hieroglyphs,
we surveyed the site perimeter, finding many additional but smaller structures.
To date, sufficient analysis has been conducted to determine that if this location
is not Site Q itself, it is nearby (Graham, 1997~. Our remote sensing imagery
suggests that there are other archeological sites in the area that we intend to visit
in the course of our research. (The difficulties of conducting ground-truth recon-
naissance in these areas are discussed later in this chapter.)
DEFORESTATION
Central America has one of the highest rates of deforestation, on a percent-
age basis, in the world (Food and Agriculture Organization, 1991~. Satellite
imagery provides the primary source of quantifiable data about forest and land-
cover changes. The remote sensing and GIS techniques used for deforestation
OCR for page 155
THOMAS L. SEVER
155
and vegetation mapping are well established (Fearnside, 1986; Sader and Joyce,
1988; Sader et al., 1990; Skole and Tucker, 1993~. These analytical techniques
have been applied to present evidence of the current deforestation threat to the
Peten region.
As noted earlier, the ancient Maya had substantially deforested the region by
the time of their collapse in the ninth century, while the current tropical forest, no
more than 1,000 years old, is being destroyed at an alarming rate in the wake of
human migration and settlement. Schwartz (1990) documents the social and
political driving forces that have affected the people and the forest of the region.
Until recently, the Peten enjoyed a largely stable sociocultural system dating
back to the 1720s. From colonial times it had been a sparsely populated region,
with one writer commenting, "After all, the Peten was then (1895) and is now
(1940) a region almost unoccupied, little developed, and of small promise" (Jones,
1940, quoted in Schwartz [1990:2411~. The region remained sparsely populated
until the 1960s, when the national government opened the Peten to colonization.
Unequal land distribution, decreasing access to land, extensive deforestation, in-
creasing economic inequality, and political unrest subsequently led to revolution.
By the late 1970s and early 1980s revolutionary guerrilla forces had estab-
lished a wide base of insurgency support against the national government in both
the Peten and the Guatemala highlands. The conflict had reached a peak by the
mid-1980s, but the struggle continued until the signing of a peace treaty between
the rebels and the government in January 1997. Between 1960 and 1986, the
Peten experienced a population increase from 26,000 to over 300,000 an in-
crease of 1,100 percent in 25 years (Schwartz, 1990:256-257~. As will be seen,
our satellite imagery demonstrates that between 1986 and 1995, human migration
and deforestation continued to accelerate.
Tropical rainforest deforestation results from complex combinations of so-
cial, economic, and biological causes. It affects the flora and fauna and the
lifestyles of indigenous populations (Nations, 1988~. Currently, cattle ranching
and slash-and-burn agriculture are the most serious threats to the Peten. Others
include road building, oil exploration, selective logging of mahogany, the taking
of endangered species of animals and birds, and the looting of archeological
treasures. Since the late 1970s, marijuana has also become an important though
illegal export crop (Schwartz, 1990:260~. These practices stand in contrast to
economic activities that have a negligible environmental impact, such as tourism
and the harvesting of chicle, xate, and pimienta.
Four Landsat TM satellite scenes were purchased for April 1986, April 1990,
May 1993, and March 1995. As with many tropical regions,
it is difficult to
acquire cloud-free data over the Peten, and these satellite scenes represent the
best data available. Image processing was conducted using Earth Resources
Laboratory Applications Software (ELAS) (Graham et al., 1985) and ERDAS
(1990) software. Data processing and analysis were conducted jointly under the
direction of Steven Sader, University of Maine, and the author. A channel 3, 4,
OCR for page 156
156
VALIDATING SOCIAL PHENOMENA, PETEN, GUATEMALA
and 5 subset was extracted from the seven-channel TM data. Atmospheric haze
was reduced by subtracting the minimum values located in deep water (Lago
Peten Itza) from the visible red (channel 3) and reflective near infrared (channel
4~. The NDVI was computed for all four dates. The equation for NDVI is:
NDVI = (near infrared - visible red)/(near infrared + visible red)
NDVI information correlates with measures of vegetation "greenness"
(Tucker, 1979; Sellers, 1985) and can easily distinguish roads, water, and sparse
vegetation from high biomass forests (Seder et al., 1991~. Change detection was
performed by subtracting the 1990, 1993, and 1995 NDVI from the 1986 NDVI.
The data were compared with false color composite images. The composites
were made by loading TM bands 4, 5, and 3 onto the red, green, and blue image
planes of the computer screen (Jensen, 1986~. In this way a time-sequence of
change from 1986 can be identified and quantified. The results are alarming for
the MBR, an area generally thought of as being protected.
Increased forest clearing can be identified throughout various parts of the
MBR. Comparison of the satellite images for the above four dates indicates that
the greatest deforestation of primary forest occurred during 1990-1993, although
the Belize-Guatemala border area saw the greatest increase during 1993-1995.
Interior roadless regions within the MBR show little or no regrowth or clearing
activity. There is a strong relationship between roads and distance to forest, with
over 90 percent of the clear cutting being conducted within 2 km of roads. What
is certain is that the ratio of clear-cutting to mature forest has been increasing
since 1986. Results indicate a general 12:1 ratio (12 ha cut to 1 ha regrown)
during 1986-1990. During 1990-1993, some areas experienced even higher ra-
tios. We are currently completing our analysis for 1993-1995, but the same
pattern of increasing deforestation is apparent as the forested landscape with
scattered agricultural fields yields to an agricultural landscape with a fragmented
forest.
Forest-clearing ratios appear to be highest in frontier areas where there are
new roads and an influx of settlers. These areas include the Sierra del Lacandon
and the Mexico-Guatemala border region in the west. Forest clearing is less
severe near lower, more stable resident populations, as in Carmelita in the central
Peten, where more traditional farming techniques are practiced. Forest clearing
is also less severe in areas where there are guards on duty, such as Tikal.
It is not simply the ratios of deforestation that are alarming, but also the
pattern of deforestation. Forest-clearing activities have created "vegetation is-
lands" of primary forest surrounded by cleared areas. These vegetation islands
are becoming more pronounced in response to new settlers and the construction
of new roads and an oil pipeline in the area (apparent in the 1995 TM image).
The extent to which this increasing deforestation is affecting the ecology of the
OCR for page 157
THOMAS L. SEVER
region, in particular the m
time.
157
.
igration routes of birds and animals, is unknown at this
What is known is that the increasing human migration into the area is adding
to the social stress as the competition for land and resources increases. Satellite
change-detection images can be used to identify potential areas of conflict as the
forces of expansion meet protected land. The peace treaty of 1997 provides for
the resettlement within the MBR of refugees who fled the area during the con-
flict. The resulting impact on the forest will be seen in future satellite images.
Between March and May 1997, there were two serious incidents inside the MBR,
in which government and nongovernmental organization (NGO) hostages were
captured at gunpoint, and a biological station was burned to the ground by a force
of 60 armed men. Eventually, the release of the hostages was negotiated, and an
agreement was made with the perpetrators to rebuild the biological station in
exchange for logging, farming, and hunting concessions within the reserve. In
May 1997, Carlos Catalan, a Guatemalan spokesman for conservation, was mur-
dered at gunpoint in the village of Carmelita. In June 1997, archeologist Peter
Mathews and his five-man research team were captured and beaten along the
Usumacinta River as they attempted to remove a Mayan altar to a local museum.
Although Matthews had the necessary government and local permissions, the
captives told him that "they don't respect any authority" (Associated Press, 1997~.
These recent incidents illustrate the reality of the situation and suggest the likeli-
hood that similar incidents will occur in the future unless an effective land-tenure
and migration policy can be established and enforced.
RESEARCH CHALLENGES:
COLLECTING GROUND-TRUTH INFORMATION
The gathering of ground-truth information, often referred to as "reference
data," involves collecting measurements or observations about objects, areas, or
phenomena that are being remotely sensed (Lillesand and Kiefer, 1994~. Social
scientists can use ground-truth information in two ways: first, it can aid in the
analysis, interpretation, and validation of the remotely sensed data; second, such
information helps in understanding the socioeconomic forces behind land-cover
modifications due to human activities.
Ground truthing is expensive and time-consuming. While the price of com-
puter hardware and software for remote sensing analysis has dropped dramati-
cally in recent years, the costs associated with ground-truth activities have gener-
ally increased. Airfare, lodging, vehicle rental, food, labor, and the like remain
expensive elements of a research design, although it may be noted that recent
advances in affordable, portable GPS receivers and digital field recorders give
the field investigator greater flexibility in the sampling design.
Our ground-truth activities require that we visit as many sites as possible in
the remote and difficult terrain of the Peten in order to document as many study
OCR for page 158
158
VALIDATING SOCIAL PHENOMENA, PETEN, GUATEMALA
sites as possible. Consequently, we tend to break camp each day and move on to
the next location. This feature of our research contrasts with the approach of
those who remain at a village or site for an extended period of time. While we
map and verify the existence of archeological features, we never excavate. Some
of the challenges we have encountered while conducting fieldwork in the Peten
include logistical problems, communication problems, equipment failure, inad-
equate maps, physical stress, suspicion, danger, and unstable political environ-
ments. In fact, our research team was captured and held at gunpoint by leftist
guerrillas for several hours before being released at nightfall.
Certain phenomena (such as prehistoric Mayan roadways) that appear in the
nonvisible bandwidths of the remote sensing data are sometimes simply not
visible from ground level and require clearing and/or excavation before being
verified. This situation is related to the fact that certain features that cannot be
seen in visible light can nevertheless be detected in the infrared or microwave
portions of the spectrum by remote sensing instrumentation (Sever, 1990~. Field
reconnaissance also provides us with other information not visible in the imag-
ery, such as the selective cutting of mahogany trees. Generally, our interviews
with local farmers and ranchers provide accurate information. Sometimes, how-
ever, the respondents provide us with either information they think we want to
hear or false information intended to mask illegal activity.
Logistics are probably the major constraint on our field work. Often we are
the first professionals to visit an unrecorded archeological site. We must sched-
ule in advance the jeeps, boats, aircraft, mules, horses, and workers that will get
us to our destination. Since many areas of the Peten do not have telephone
service, a member of our team who lives in Guatemala must travel weeks and
months in advance to arrange these rentals with the local villagers. The more
inaccessible the location, the more difficult the arrangements are. Generally, our
field missions last 2 to 3 weeks. As we travel and switch from jeeps to boats to
horses and mules, it is critical that the dates, times, and locations for these ar-
rangements be finalized in advance.
Occasionally, we are met with suspicion regarding the true purpose of our
research. We have successfully combatted this situation by taking the time to
explain our research goals and objectives to the local residents. We always take
a large number of satellite images and, after explaining how we are using the
imagery, leave a copy of it with the personas) involved. Through years of expo-
sure and word of mouth, we have gained acceptance and support for our data
acquisition activities, as well as the confidence of the inhabitants. As the years
have passed, many of the inhabitants have become better educated about satellite
imagery and GPS units, so that when we stop in a village and present the images,
they can often help us interpret some of the features and anomalies displayed.
Having a Guatemalan national on the research team is also a positive benefit to
our research activities.
GPS measurements are a critical component of our field research. Initially,
OCR for page 159
THOMAS L. SEVER
159
in 1988, there were only a few satellites in orbit, and we often found ourselves
climbing a temple at midnight to collect a position that would be available only
between 1:00 and 4:00 a.m. Also, intense vegetation cover of the tropical forest
limited the collection of GPS readings. Today there is a complete constellation of
satellites, and readings can be gathered nearly around the clock. New GPS units
with better software allow for the collection of more data with greater accuracy.
A problem we often encounter is the inaccuracy of available maps. We
consistently find that lakes, rivers, archeological sites, and cultural features are
not located where the map indicates. Apart from the obvious in-field confusion,
there is the major concern that if these inaccurate maps are digitized and incorpo-
rated into a GIS, they will lead to false results for predictive models. We resolve
this dilemma by constantly comparing our GPS measurements, imagery, and
maps to eliminate as much confusion as possible. It should also be noted that the
names on a map are not necessarily the names used by the local inhabitants.
As we studied deforestation trends in the Peten over the last several years, we
designed our ground-truth activities primarily to identify the difference between
new forest clearings and regrowth. Now we are expanding our ground-truth
activities to include information on the decision processes associated with land
use and land conversion. Currently, the various socioeconomic factors associ-
ated with deforestation are poorly understood. In addition, much of the current
uncertainty involved in modeling the terrestrial carbon budget arises from inad-
equate data on tropical deforestation rates and trends in land-use conversion. To
address these scientific issues, we will acquire additional information as we
interview local farmers and ranchers. Through these interviews, we will deter-
mine such factors as the crop-to-fallow ratios, the decision process for converting
land to pasture or to shifting agriculture, the forest fragmentation indices and
spatial characteristics of cleared land, the associated socioeconomic factors, and
how the driving forces differ by zones or management units. The results will be
correlated over the time scale of our database, providing better analytical infor-
mation for management decisions.
SUMMARY AND CONCLUSIONS
The delicate ecosystem of the MBR in the Peten region of northern Guate-
mala was managed successfully for centuries by the ancient Maya until their
collapse in the ninth century A.D. The archeological evidence indicates, how-
ever, that by the time of their collapse, the Maya had deforested most of the
region. For the next 1,000 years the forest regenerated. Today, human migration
and so-called "modern" subsistence techniques once again threaten the sustain-
ability of the area.
Through the use of remote sensing and GIS research, we are attempting to
answer questions about the past in order to protect and manage the resources of
the future. The protection of the tropical rainforest is also synonymous with the
OCR for page 160
160
VALIDATING SOCIAL PHENOMENA, PETEN, GUATEMALA
protection of archeological sites, for the cutting and burning of an area destroy
not only the trees, but also archeological features and materials. In addition, the
construction of modern roads and pipelines provides a conduit for the illegal
looting of endangered animal species and archeological treasures.
Remote sensing data have successfully located archeological features in the
Peten region that are difficult to discern from traditional survey and analysis
techniques. These features include ancient roadways, temples, cisterns, and agri-
cultural areas. The detection and subsequent analysis of these features may help
answer questions regarding ancient Mayan subsistence, transportation, and water
management and the factors that led to the eventual abandonment of the area at
the time of the Mayan collapse. At the same time, however, verification of
archeological features detected in the remote sensing data is expensive, time-
consuming, difficult, and dangerous because of the dense vegetation, remoteness,
and hazards associated with the Peten landscape.
After the ninth century, the Peten remained a sparsely populated area until
the Guatemalan government opened the area to colonization in the 1960s. Since
that time the forest has continued to be cut down at an accelerating rate as human
migration and settlement have introduced nontraditional agricultural techniques.
The driving forces behind deforestation activities in the region result from a
complex combination of social, economic, and political issues. Change-detec-
tion analysis using remote sensing imagery has been used to document and quan-
tify the extent and rate of change during 1986-1995. Data analysis reveals that
the ratio of clear-cutting to mature forest has been increasing over that time. The
highest forest-cutting ratios are associated with the construction of new roads and
increases in migrating settlers. Forest-clearing ratios are lowest near resident
populations who practice traditional farming techniques. Cattle ranching and
slash-and-burn agriculture are the greatest threats to the Peten, although road
building, oil exploration, selective logging of mahogany, and illicit crops also
adversely impact the ecology of the region.
Increasing human migration and settlement in the next few years will only
add to the deforestation and social stress as the competition for resources in-
creases. According to current estimates, only 2 percent of the Peten's forest will
survive by the year 2010. The use of aerial and satellite imagery can help identify
areas of possible conflict, inventory natural and cultural resources, identify ille-
gal practices, and monitor protected areas. It is hoped that the results of this
interdisciplinary research will provide information that will help managers, sci-
entists, and politicians responsible for the MBR and the Peten region in general
make more informed decisions and thereby avoid the collapse that occurred in
this area a little over 1,000 years ago.
OCR for page 161
THOMAS L. SEVER
REFERENCES
Adams, R.E.W., T.P. Culbert, W.E. Brown, P.D. Harrison, and L.J Levi
1990 Rebuttal to Pope and Dahlin. Journal of Field Archaeology 17:241-243.
Associated Press
1997 Archeologists barely survive ambush in Mexican jungle. CON Interactive World News,
July 1.
Cahuec, E., and J. Richards
1994 La variacion sociolinguistica del Maya Q'eqchi. Boletin Linguistico 40 Guatemala.
Canteo, C.
1996 Destruccion de Biosfera Maya avanza ano con ano. Siglo Veintinno (Guatemala), Novem-
ber21.
Culbert, T.P.
1993 Maya Civilization. Washington, D.C.: St. Remy Press and Smithsonian Institution.
1974 The Lost Civilization: The Story of the Classic Maya. New York: Harper and Row.
Culbert, T.P., L. Levi, B. McKee, and J. Kunen
1995 Investigaciones Arqueologicas en el Bajo La Justa, Entre Yaxha y Nakun. Unpublished
field report, Department of Anthropology, University of Arizona.
Curtis, J.H., D.A. Hodell, and M. Brenner
1996 Climate variability on the Yucatan Peninsula (Mexico) during the past 3500 years, and
implications for Maya cultural evolution. Quaternary Research 46, Article No. 0042:37
47.
ERDAS
1990 Field Guide, Version 7.4. ERDAS, Inc., Atlanta, Ga.
Fearnside, P.M.
1986 Spatial concentration of deforestation in the Brazilian Amazon. Ambio 15:74-81.
Food and Agriculture Organization
1991 Second Interim Report on the State of Tropical Forests. Unpublished paper, Forest Re-
sources Assessment 1990 Project, United Nations FAO, Rome, Italy.
Graham, I.
1997 Mission to La Carona. Archaeology, September/October:46.
Graham, M.H., B.G. Junkin, M.T. Kalcic, R.W. Pearson, and B.R. Seyfarth
1985 Earth Resources Laboratory Applications Software (ELAS), Revision 3. NASA-NSTL-
Earth Resources Laboratory, Report No. 183, Stennis Space Center, Miss.
Hammond, N.
1990 Ancient Maya Civilization. New Brunswick, N.J.: Rutgers University Press.
Jensen, J.R.
1986 Introductory Image Processing-A Remote Sensing Perspective. Englewood Cliffs, N.J.:
Prentice-Hall.
Jones, C.L.
1940 Guatemala: Past and Present. Minneapolis: University of Minnesota Press.
Kelley, P.S.
1983 Digital analysis in remote sensing: from data to information. Pp. 218-240 In Remote
Sensing of the Environment, B.F. Richason, Jr. ed.
Lillesand, T.M., and R. Kiefer
1994 Remote Sensing and Image Interpretation. New York: John Wiley and Sons.
Lundell, C.L.
1937 The Vegetation of the Peten. Carnegie Institute Publication No. 478, Washington, D.C.
Nations, J.
1988 Tropical Rainforest: Endangered Environment. New York: Franklin Watts.
161
OCR for page 162
62
VALIDATING SOCIAL PHENOMENA, PETEN, GUATEMALA
Pope, K.D., and B.H. Dahlin
1989 Ancient Maya wetland agriculture: New insights from ecological and remote sensing.
Journal of Field Archaeology 16:87-106.
Radar detection and ecology of ancient Maya canal systems. Journal of Field Archaeol-
ogy 20:379-383.
Rice, D.S.
1991 Roots. Natural History February:10-14.
Sabloff, J.A.
1995 Drought and decline. Nature 375: 357.
Sader, S.A.
1995 Spatial characteristics of forest clearing and vegetation regrowth as detected by Landsat
Thematic Mapper imagery. Photogrammetric Engineering and Remote Sensing 61: 1145-
1151.
Sader. S.A., and A.T. Joyce
1988 Deforestation rates and trends in Costa Rica, 1940-1983. Biotropica 20(1): 11-19.
Sader, S.A., T.A. Stone, and A.T. Joyce
1990 Remote sensing of tropical forests: an overview of research and applications using non-
photographic sensors. Photogrammetric Engineering and Remote Sensing 55(10):1343-
1351.
Sader, S.A., G.V.N. Powell, and J.H. Rappole
1991 Migratory bird habitat monitoring through remote sensing. International Journal of Re
mote Sensing 12(3):363-372.
Sader, S.A., T. Sever, J.C. Smoot, and M. Richards
1994 Forest change estimates for the northern Peten region of Guatemala 1986 to 1990. Hu
man Ecology 22(3):317-322.
Sader, S.A., T. Sever, and J.C. Smoot
1996 Time series tropical forest change detection: A visual and quantitative approach. Interna-
tional Symposium on Optical Science, Engineering and Instrumentation, Denver, Colo.
SPIE, Volume 2818-2-12.
Schuster, A.M.H.
1997 The search for Site Q. Archaeology September/October:42-45.
Schwartz, N.B.
1990 Forest Society: A Social History of Peten, Guatemala. Philadelphia: University of Penn-
sylvania Press.
Sellers, P.J.
1985 Canopy reflectance, photosynthesis and transpiration.
Sensing 6(8):1335-1372.
International Journal of Remote
Sever, T.
1990 Remote Sensing Applications in Archeological Research: Tracing Prehistoric Human
Impact Upon the Environment. Ph.D. dissertation, University of Colorado, Boulder.
Available: University Microfilms, Ann Arbor, MI.
Sheets, P., and T. Sever
1988 High tech wizardry. Archaeology 41(6) Nov/Dec:28-35.
Skole, D., and C. Tucker
1993 Tropical deforestation and habitat fragmentation in the Amazon: Satellite data from 1978
to 1988. Science 260: 1905-1910.
Stuart, G.E.
1991 Maya heartland under siege. National Geographic 10:94-107.
Trombold, C.D.
1991 Ancient Road Networks and Settlement Hierarchies in the New World. Cambridge, En-
gland: Cambridge University Press.
OCR for page 163
THOMAS L. SEVER
163
Tucker, C.J.
1979 Red and photographic infrared linear combinations for monitoring vegetation. Remote
Sensing Environment 8:127-150.
Turner II, B.L.
1993 Rethinking the "new orthodoxy:" Interpreting ancient Maya agriculture. Pp. 57-88 In
Culture, Form, and Place: Essays in Cultural and Historical Geography, K. Mathewson,
ed. Geoscience and Man 32. Baton Rouge, La.: Louisiana State University.
Representative terms from entire chapter:
social phenomena
