The use of geospatial technologies for identification of clandestine cemeteries

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The use of geospatial technologies for identification of clandestine cemeteries: A pilot study for the Pueblo Bello case in the department of Córdoba, Colombia May 25, 2006 Introduction The use of geospatial technologies, particularly remote sensing, has proven a useful tool in the location of sites of archaeological interest (Banning 2002), as well as in the detection of gravesites containing human remains (Davenport 2001; Killam 2004). More recently, an application of these technologies has permitted the location of mass graves sites in conflict areas of the world. These mass gravesites contain the remains of dozens, and sometimes hundreds, of individuals disappeared in conflicts, such as in the former Yugoslavia (Hunter et al. 2005)1. Electronic mapping techniques using GIS systems have also taken place in countries such as Cambodia, where experts have mapped mass graves sites created under the Pol Pot regime (Etcheson 1999). EQUITAS proposes the combined use of remote sensing information, as well as GIS and geophysical technologies (such as magnetometers and gradiometers) on the ground, as a potential methodology for the location of mass graves sites in Colombia. The unique modus operandi of disappearances in Colombia, matched with its geographic conditions and conflict situation, make the use of geospatial technologies a valuable alternative in identifying clandestine cemeteries in this country’s context. Together with electronic mapping systems, these also allow for a mapping of these cemeteries, and by de facto, the Colombian conflict. The Pueblo Bello Case In January 1990, paramilitaries under Fidel Castaño Gil2 abducted and disappeared 43 campesinos (peasants) from the town of Pueblo Bello, department of Antioquia. The campesinos were taken to Fidel Castaño’s hacienda, known as Las Tangas, located in the outskirts of the city of Montería, in the neighboring department of Córdoba. Witness testimonies state that these campesinos were allegedly tortured and assassinated, before being buried in mass graves at Las Tangas, near the banks of the Sinú river, in an area knows as “Playa Caudillo”. In April 1990, Colombian police carried out an exhumation in Las Tangas, using heavy machinery, where the remains of 24 men were allegedly recovered. All of the remains were badly destroyed due to the effects of the heavy machinery. Six were identified by visual recognition, while the remaining eighteen were subsequently buried as NNs in a cemetery in Montería. Since 1990, there have been two government-led investigations (in 2005 and 2006 respectively) in Las Tangas, all of which have been unsuccessful in finding the remains linked to this case. The Inter-American Court for Human Rights has recently rules against the Colombian government in the Pueblo Bello case, and identified judicial authorities as negligent, not only in the obviously poor recovery of remains in situ in Las Tangas, but also in the ensuing handling of the bodies taken to Montería3.


For more information, please refer to “Experts investigate new methods of using satellite images to locate mass grave sites,” The Associated Press, May 31, 2005 and “New way to find mass graves in Bosnia,” The Associated Press, August 17, 2005. See also International Commission on Missing Persons, “ICMP finds improved methods for locating mass graves,” Press release, August 16, 2005. Available at <> 2 Fidel Castaño Gil, along with Carlos and José Vicente Castaño Gil, are the founders of the Peasant Self-Defense Forces of Cordoba and Uraba (ACCU), a right-wing paramilitary organization that began in the early 1990s and later became the United Self-Defense Forces of Colombia (AUC). 3 Corte Interamericana de Derechos Humanos. Sentencia Caso de la Masacre Pueblo Bello vs. Colombia, January 31, 2006, paragraphs 173-178.

Given Fidel Castaño Gil’s long record of criminal activity, it is expected that the victims of the Pueblo Bello case are not the only individuals buried at Las Tangas. It is likely that this hacienda holds the remains of many other individuals disappeared prior and after 1990. The Colombian context The Pueblo Bello case is representative of many disappearances carried out by armed actors in Colombia. For decades, all Colombian armed factions—paramilitaries, guerrillas, and the Colombian armed forces—have regularly deposited the remains of their victims in mass graves throughout the country (Gómez López and Patiño Umaña 2006). While all mass graves make for demanding recovery and tasks, there is an additional characteristic of mass graves in Colombia that makes these particularly difficult: Colombian gravesites are often formed by the gradual and systematic burials in one location over an extended period of time, and not the collective burial of many individuals at one time. People from different places in one general region are individually and systematically killed by armed factions, and are buried in areas selected by these groups. These areas tend to be located in specific rural strongholds, such as haciendas (large estates, often for livestock or agricultural plantations) or encampments. As time goes by and cases accumulate, these locations become clandestine cemeteries, holding the remains of dozens, perhaps hundreds, of disappeared individuals. This modus operandi by armed actors, and the subsequent phenomenon of clandestine cemeteries, has become increasingly public in Colombia, garnering the attention of international institutions such as the United Nations4. In April 2006, governmental authorities discovered one of Colombia’s largest mass gravesites to date—La Gabarra, a town in the department of Norte de Santander. From the late 1990s to date, hundreds of individuals were disappeared by paramilitaries and buried in this site. To date, 179 people have been recovered, and investigations are ongoing. Yet La Gabarra is not an isolated incident. In March 2005, governmental authorities discovered one of Colombia’s largest mass gravesites to date—San Onofre. From the late 1990s to date, hundreds of individuals were disappeared by paramilitaries and buried in an hacienda located in the town of San Onofre, in the department of Sucre5. There have also been other mass graves recently been recently discovered in banana and African palm plantations in the town of Ciénaga, department of Magdalena6. Rural clandestine cemeteries are one of the hallmarks of the Colombian conflict. While in other conflicts there are intense periods of collective disappearances that lead to the formation of large mass graves, such as in Cambodia or the former Yugoslavia, Colombia’s protracted and low-intensity conflict favors individual yet systematic disappearances that gradually form clandestine cemeteries in the countryside. Although the final result in both situations is a mass grave site, Colombia’s clandestine cemeteries hold unconnected episodes of individual disappearances that take place throughout a number of years, only related by the acts of perpetrators who bury them in the same specific site. Applying geospatial technologies in Colombia The applications of geospatial technologies hold a number of advantages for the Colombian context. As follows:


The 2005 UN Report of the High Commissioner for Human Rights on the Situation of Human Rights in Colombia states that allegations of forced disappearances became “more evident a certain time after the events, through the discovery of clandestine graves, individual or collective, such as those of Salazar, Sardinata, and in the rural area of Cucutá (Norte de Santander) and in San Onofre (Sucre).” See E/CN.4/2006/9, January 20, 2006, Annex III, paragraph 31. See also the UN Working Group on Enforced and Involuntary Disappearances’ 2006 Mission to Colombia: “Reportedly, thousands of graveyards containing bodies of missing and disappeared persons still exist all over the country. Apparently, information gleaned from the general public about such graves reveals a more widespread pattern than previously known.” See E/CN.4/2006/56/Add.1, IV D, Paragraph 51. 5 For more information, please refer to the article by Juan Forero “Colombia unearthing plight of its disappeared,” The New York Times, August 10, 2005. Also see “La hacienda El Palmar, en San Onofre (Sucre), está sembrada de historias del terror paramilitar,” El Tiempo [Colombian national newspaper], April 17, 2005. 6 For more information, please refer to “Mass graves unearthed in Colombia,” BBC News, February 15, 2006 and “Los restos oseos de 20 personas fueron encontrados en diferentes fosas comunes en Tucurinca,” El Tiempo [Colombian national newspaper], February 12, 2006.

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Remote-sensing technologies (particularly through the use of high resolution satellite images) allows to determine areas of disturbance in vegetation and surface composition that could be consistent to mass grave sites, providing information difficult to obtain with solely a pedestrian survey. Geophysical technologies (such as magnetometer and gradiometer) allows for the confirmation of soil alterations in potential disturbance sites. Both of these technologies are non-invasive techniques that can help detect, that do not alter or destroy clandestine cemetery sites. Remote-sensing images (in conjunction with aerial photography) allow a close, chronological monitoring of gradual clandestine cemetery site formation.

The application of geospatial technologies to these areas is ideal in many conflict areas of Colombia, where large extensions of uncultivated plains and or livestock pasture areas are controlled by armed factions, such as in the Pueblo Bello case. Methodology used in the Pueblo Bello case The Pueblo Bello case was a first attempt to use of remote-sensing data and pedestrian survey. The initial approach, carried out in June 2005, was to interpret low-resolution data from 2002 (LANDSAT 7 images enhanced 14m/pixel 4,5,3 composition, see Figure 2 and Figure 4) of Playa Caudillo and obtain a general understanding of topography and land use. Patterns of erosion were interpreted as disturbances and plots of dense vegetation were also identified. This data was subsequently interpreted along with additional information from complementary historical image data from satellite images of Playa Caudillo from 1991 (see Figure 2, B). A thematic map7 was produced and compared to testimonial data and hand-drawn maps from a deceased witness. The result of this analysis was the selection of a high-potential area within the thematic map of five square kilometers, where soil disturbances matched testimonial and witness information. Information from a field visit in August 2005 carried out by Colombian authorities and EQUITAS’ staff helped make this information more robust. This map confirmed that, within the general high-potential area, there were two sectors of interest: the Playa Caudillo Sector and the Southern Sector (Figure 1). In January 2006, high-resolution Quickbird images allowed to further confirm these two sites, where intense Colombian authorities and EQUITAS’ staff carried out archaeological prospection and 6,000 test pits were made in the Playa Caudillo Sector (see Figure 1, Site 2 and 5). The high-resolution Quickbird images also confirm that part of the site was eroded by the river between 1989 and 2005 (see Figure 1). The Southern Sector (see Figure 1) was not as intensely surveyed. Only 60 test pits were made, yet this area yielded a single grave with three individuals (see Figure 1, Site 6)—a finding that strongly suggests that Las Tangas contains more gravesites outside Playa Caudillo. The pedestrian survey also identified multiple surface disturbances, like those at the site where the three skeletons were found. However, few of these features were excavated. Thus, the Southern Sector (see Figure 1) is a location with a very high probability for the recovery of human remains. It is worth noting that this location presents a distinct land coverage pattern: an intense vegetation growth that has taken place in the last 18 years. Results The two main questions for the Pueblo Bello case were: 1) the identification and sampling of soil disturbance sites that could indicate potential gravesites in Playa Caudillo, which yielded a negative result, and 2) tracking changes in the course of the Sinú river to determine if gravesites were altered (and remains potentially lost) from fluvial changes. This was a strong hypothesis, given that the proximity of the burials to the Sinú riverbanks may have caused them to be destroyed by erosion. 7

A thematic map shows the spatial distribution of one or more specific data themes for standard geographic areas

However, findings from satellite images show that this hypothesis is not the case. The 2006 Quickbird image (Figure 3) shows soil disturbances and/or man-made alterations in Playa Caudillo and other related sites. Each site on the map is matched with a picture that illustrates ground-level findings. Historical image date helped track the course of the SinĂş River, creating a map that accounts for areas severely modified by the river in the last 18 years (see Figure 1). Thus, the main result is that the Southern Sector, where gravesites were found (Figure 1, Site 6) has not been altered, and also presents a distinct pattern of vegetation growth. Conclusion Although gravesites were not found in the Playa Caudillo Sector, the application of geospatial technologies in the Pueblo Bello case and its analysis have been useful in understanding the potential distribution of gravesites in relation to land cover data in this area. The Playa Caudillo Sector (Figure 1) yielded no evidence, yet the Southern Sector contained a mass grave with three individuals (Figure 1, Site 6). Further investigations need to be carried out in the Southern Sector, taking the aforementioned findings into account. A comparison of the 1989 and 2005 images suggests that the Southern Sector was intentionally abandoned and vegetation was let to overgrow, helping facilitate the concealment of gravesites. A pattern of abandonment of land plots could be part of the modus operandi of paramilitary groups, a hypothesis that could be further explored with a combination of remote sensor data and field data recovery procedures. Several plots of abandoned land have been already identified (see Figure 4). The efficiency and effectiveness of forensic archaeological investigation of areas suspected to contain clandestine cemeteries in Colombia can be greatly enhanced though interpretation of remote sensor data, as well as the implementation of geophysical surface and subsurface search procedures. Geo-referenced databases that document this evidence can further guide search parties into areas that may be ignored otherwise, and reduce the dependency on inaccurate (and often misleading) testimonial data.

Figure 1. Geographic changes SinĂş River using satellite and aerial photography, 1989-2006

Figure 2. Series of satellite images and aerial photographs documenting changes in the Sinú River’s course and surrounding areas

A. 1989: Aerial photograph of Playa Caudillo. Instituto Geográfico Agustín Codazzi (Colombia)

C. 2002: Low 24 m. resolution LANDSAT image, Bands 4,5,3 composition.

B. 1991: LANDSAT Image (1054). SIMCI Project, UN Office on Drugs and Crime Prevention (Colombia)

D. 2006: High resolution (64 cm.) Quickbird image, Green, blue and IR bands.

Figure 3. 2006 High-resolution satellite imagery (annotated with photographs and captions of groundlevel findings)

Site 1: Abandoned concrete house used as a campsite.

Site 2: Beach area of approximately 700 meters.

Site 3: Wooded area described by Colombian officials, were the April 1990 exhumations took place

Site 4: Small barren island, easily flooded and covered with light vegetation.

Site 5: Crop area, marked on the map by a dotted line. This area was intensely surveyed.

Site 6: Wooded area located 600 meters southeast from the crop area, where soil disturbances were found.

Point A: Isolated areas marked as potential survey site through satellite imagery. In this area a small road was found that bordered the river’s previous course. Site 6: Site with three adult skeletons found in an area of soil disturbance. All three skeletons had signs of gunshot wounds to the head and torture.

Point B: Soil disturbance areas were in an area near a large tree, were test pits were carried out, with negative results.

Point C: Man-made alterations are found along the old road next to the river’s old course.

Point D: Isolated area with a circular soil elevation. Test pits carried out provided negative results.

Point E: Isolated area where a piece of clothing was found in test pits carried out in August 2005.

Point E: Focus on this isolated area, where no changes in stratigraphy are seen and no evidence has been found.

Figure 4. Preliminary supervised classification of Landsat image showing land cover

Key Unclassified Cloud and deep water Tall forest Tall humid forest, manioc and banana. Dry grass 1 Dry grass 2 SinĂş River Middle size forest Tall humid grass Short humid grass Sandy beach

References cited Banning, EB. 2002. Archaeological Survey: Manuals in Archaeological Method, Theory and Technique. New York: Kluwer Academic/ Plenum Publishers. Davenport, GC. 2001. Remote sensing applications in forensic investigations. Historical Archaeology, 35(1), pp. 87-100. Etcheson, C. 1999. Mapping Project—The Number: Quantifying Crimes Against Humanity in Cambodia. Phnom Penh: Documentation Center of Cambodia. Gómez López, AM and A Patiño Umaña. 2006. Who is missing? Problems in the application of forensic archaeology and anthropology in Colombia’s conflict. In R Ferllini (Ed.), Forensic Archaeology and Human Rights, Springfield: Charles C. Thomas Publisher. [Under review for publication]. Hunter JR, M Karaska, JBT Scott, EA Tetlow, and A Reddick. 2005. The Identification of Mass Graves in the former Yugoslavia using Geophysics and Remote Sensing. Sarajevo: International Commission for Missing Persons. Killam, EW. 2004. The Detection of Human Remains. Springfield: Charles C. Thomas Publisher.

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