This is the accessible text file for GAO report number GAO-03-319R 
entitled 'Drug Control: Coca Cultivation and Eradication Estimates in 
Colombia' which was released on January 08, 2003.

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January 8, 2003:

The Honorable Charles H. Taylor:

House of Representatives:

Subject: Drug Control: Coca Cultivation and Eradication Estimates in 


Dear Mr. Taylor:

Colombia is the world’s leading producer and distributor of cocaine and 

a significant supplier of heroin to the United States. According to the 

Department of State, Colombia provides about 90 percent of the cocaine 

entering the United States and approximately two-thirds of the heroin 

found on the East Coast. A key objective of the U.S. counternarcotics 

strategy is to assist Colombia in its efforts to reduce the amount of 

illicit drug crops being cultivated in the country. Under the 

Department of State’s Bureau for International Narcotics and Law 

Enforcement Affairs, the Office of Aviation supports the Colombian 

National Police’s efforts to eradicate coca and opium poppy through 

aerial eradication.[Footnote 1]

In March 2002, the Executive Office of the President, Office of 

National Drug Control Policy (ONDCP), reported that coca cultivation in 

Colombia increased by 25 percent between 2000 and 2001--from 136,200 

hectares[Footnote 2] to 169,800 hectares--despite Colombian 

eradication efforts. These estimates were prepared by the U.S. Director 

of Central Intelligence, Crime and Narcotics Center (CNC).[Footnote 3] 

However, U.S. Embassy in Bogotá officials questioned the reported 

increase, noting that the number of hectares of coca the Office of 

Aviation estimated eradicated in 2001 had increased substantially over 

previous years.[Footnote 4] As the result of earlier concerns about the 

coca cultivation estimates in Colombia, in November 2001, ONDCP had 

initiated an evaluation of CNC and the Office of Aviation methodologies 

for estimating coca cultivation and eradication, respectively. ONDCP 

completed its study in June 2002 and made a number of recommendations 

to improve both estimates.

In your letter to us, you noted the differing coca estimates for 

Colombia. In subsequent discussions with your staff, we agreed to 

determine the (1) purposes of CNC’s coca cultivation estimate and the 

Office of Aviation’s coca eradication estimate in Colombia and (2) 

status of actions to implement the ONDCP study’s recommendations. To 

address these objectives, we reviewed relevant documentation and met 

with cognizant officials from ONDCP, CNC, and the Office of Aviation.

Results in Brief:

The coca cultivation estimate prepared by CNC and the coca eradication 

estimate prepared the Office of Aviation in Colombia serve different 

purposes and cannot be readily reconciled to one another because of 

differences in their respective methodologies.

² Annually, CNC develops cultivation estimates for coca, opium poppy, 

and marijuana in drug-producing countries around the world. These are 

published each March as part of the President’s determination whether 

to continue providing U.S. assistance to major drug-producing and -

transit countries. To prepare its estimates, CNC analyzes black and 

white high-resolution photographs taken primarily from satellites 

covering a representative sample of the target country’s known or 

suspected drug-growing areas. This allows CNC to estimate illicit drug 

cultivation for the entire country. In Colombia, these images are 

usually taken, weather permitting, between November and January of each 

year. Because these cultivation estimates are used by other U.S. 

government agencies to help determine the amount of illicit drugs 

available for consumption in the United States, CNC focuses on 

identifying fields of healthy coca plants with leaves that are suitable 

for processing into cocaine.

² As part of its support for the Colombian National Police, the Office 

of Aviation uses airborne digital cameras to photograph coca fields for 

targeting aerial spraying and, afterwards, to help estimate the number 

of hectares eradicated. Through computer analysis, the Office of 

Aviation analyzes the light reflecting off the vegetation to identify 

coca. The digital photos can be taken anytime weather permits and are 

targeted over areas where the Colombian National Police intends to 

conduct or has conducted aerial eradication operations. Also, because 

the Office of Aviation wants to identify any coca fields for aerial 

eradication, it includes coca seedlings and mature, damaged, and dead 

plants in its definition of a coca field.

The June 2002 ONDCP study recommended, among other things, that CNC and 

the Office of Aviation reconcile their definitions of a coca field, 

develop an error rate for each estimate, and enhance the technologies 

used for developing the respective estimates. Both CNC and Office of 

Aviation officials said they are in the process of implementing many of 

these recommendations, though the Office of Aviation said that some 

would require additional funding. CNC noted that it would have many of 

the changes necessary completed in time for its 2002 coca cultivation 

estimate. As a result of CNC’s and the Office of Aviation’s continuing 

efforts to address ONDCP’s concerns, we are not making any 

recommendations at this time.


Recognizing the seriousness of illegal drug activities in Colombia, the 

Colombian government, in October 1999, announced a $7.5 billion 

counternarcotics plan known as Plan Colombia. Among other things, Plan 

Colombia proposed to reduce the cultivation, processing, and 

distribution of illicit narcotics by 50 percent over 6 years. Achieving 

this goal included undertaking a substantially increased aerial 

eradication program in the primary coca-growing regions of Colombia. In 

July 2000, the United States provided about $1.3 billion to Colombia, 

other Andean countries, and U.S. agencies involved in drug interdiction 

and law enforcement. In fiscal year 2002, the United States provided 

Colombia more than $550 million for counternarcotics-related 

activities; for fiscal year 2003, the administration has requested 

about $670 million in additional assistance to address many of these 

same purposes.

With the large infusions of counternarcotics funding into Colombia, 

officials at the U.S. Embassy in Bogotá expected to demonstrate 

progress in reducing the amount of coca being cultivated in Colombia. 

However, as the following table indicates, CNC’s 2001 estimate showed 

an increase in coca cultivation of almost 25 percent.[Footnote 5] As 

noted by the embassy, the CNC estimated increase occurred despite the 

number of hectares estimated eradicated (per year) increasing 

substantially in 2001 compared with recent prior years.

Table 1: Hectares of Coca Estimated under Cultivation and Eradicated in 

Colombia, 1998-2001:

: Crime and Narc; : otics Center; : Office of Aviation.

Year; Hectares under cultivation; Percent increase; Hectares 


1998; Hectares under cultivation; 101,800; Percent increase; 28;

Hectares eradicated; 49,641.

1999; Hectares under cultivation; 122,500; Percent increase; 20; 

Hectares eradicated; 39,113.

2000; Hectares under cultivation; 136,200; Percent increase; 


increase; 11; Hectares eradicated; 42,283.

2001; Hectares under cultivation; 169,800; Percent increase; 25; 

Hectares eradicated; 77,165.

[End of table]

Source: CNC figures are from its report titled Latin American Narcotics 

Cultivation and Production, Estimates 2001 (Washington, D.C.: March 

2002). The Office of Aviation figures were provided by its headquarters 

office at Patrick Air Force Base, Florida.

In March 2002, the U.S. Embassy in Bogotá stated that the CNC estimates 

were “very wide of the mark and the apparent result of years of chronic 

underestimation of the amount of coca being cultivated in 

Colombia.”[Footnote 6] According to the embassy, CNC did not account 

for significant aerial eradication operations that occurred in southern 

Colombia during late 2001.[Footnote 7] CNC officials said that CNC 

alerted its customers that the 2001 annual estimate did not reflect the 

eradication activity. In addition, when CNC’s coca cultivation 

estimates for Colombia were publicly released, ONDCP noted that any 

coca killed by aerial eradication operations conducted after CNC’s 

satellite imagery was taken was not accounted for.[Footnote 8]

Purposes of Coca Cultivation and Eradication Estimates:

CNC and the Office of Aviation have very different purposes in 

developing their respective estimates for coca cultivation and 

eradication. CNC’s primary purpose is to determine how much coca, on an 

annual basis, is available for processing into cocaine. The Office of 

Aviation’s primary purpose is to identify coca fields for aerial 

eradication and then to assess the effectiveness of the spray 

operations. The technologies used reflect these differences. CNC 

obtains most of its information through satellites and uses a random 

sampling technique to estimate coca cultivation countrywide. The Office 

of Aviation uses aircraft mounted multi-spectral[Footnote 9] digital 

cameras to photograph designated areas suspected of coca cultivation.

CNC’s Coca Cultivation Estimates:

The Foreign Assistance Act of 1961, as amended, requires that for major 

drug-producing and -transit countries to receive U.S. assistance, the 

President must annually certify that they are cooperating with the 

United States to reduce the production and flow of illegal drugs into 

the United States.[Footnote 10] In March of each year, as part of the 

certification process, the State Department publishes the International 

Narcotics Control Strategy Report that describes the major 

drug-producing and -transit countries’ counternarcotics efforts and, 

among other things, reports the amount of illicit narcotics being 

cultivated based on CNC estimates.

CNC has been involved in estimating crop cultivation for more than 30 

years. In the late 1960s, it began developing imagery-based statistical 

techniques that, by the 1970s, were used to estimate grain production 

in the Soviet Union. In 1985, CNC began using these techniques to 

estimate coca cultivation and, by 1990, it used them to develop 

worldwide illicit crop estimates. CNC’s annual cultivation estimates 

are designed to provide U.S. decision makers an estimate of the amount 

of illicit drugs being cultivated worldwide and serve as the basis for 

estimating the amount of illicit narcotics available for consumption in 

the United States. CNC’s estimates are not designed to quantify or 

account for activities such as eradication or replanting that may take 

place throughout the year.

In preparing its Colombian estimate, CNC develops a statistical sample 

of known and suspected coca-growing areas. CNC relies primarily on 

high-resolution satellite imagery of these areas, but also uses 

commercial satellite imagery and aerial photographs. CNC selects 

targets to analyze based on prior history and information from other 

sources, including the Office of Aviation and the Department of 

Defense. The satellite imagery is black and white photographs that are 

usually taken, weather permitting, in November through January each 

year to allow time for them to be analyzed and the results incorporated 

into the annual March report. Because CNC’s coca cultivation estimates 

are used to help determine the amount of cocaine available for 

consumption in the United States, CNC focuses on identifying healthy 

coca plants with leaves that are suitable for harvesting and processing 

into cocaine.

The Office of Aviation’s Coca Eradication Estimates:

Under Section 481 of the Foreign Assistance Act of 1961, as 

amended,[Footnote 11] the State Department provides assistance to 

various drug-producing and -transit countries to support their efforts 

in reducing drug-trafficking, production, and related:

activities. As part of this assistance, the Office of Aviation has 

supported the Colombian National Police in conducting aerial 

eradication missions since 1995.

In 1998, the Office of Aviation began using two airborne multi-spectral 

high-resolution digital cameras to photograph and locate coca fields in 

Colombia. Through sophisticated computer analysis of the light 

reflecting off the ground vegetation, the Office of Aviation is able to 

identify suspected coca fields for planning spray missions. After the 

fields have been sprayed, the targeted areas are often photographed 

again to help the Office of Aviation estimate how much of the coca has 

been eradicated.[Footnote 12] The Office of Aviation also applies an 

effectiveness factor or “kill rate” to the fields sprayed to estimate 

how much coca was eradicated.[Footnote 13] In identifying coca fields, 

the Office of Aviation includes coca seedlings, mature coca, coca that 

may be dying or dead because of spray operations, and unkempt coca 

(fields of irregular size and shape not neatly maintained).

The ONDCP Study:

In November 2001, ONDCP initiated an evaluation of CNC’s methodology 

for estimating coca cultivation and the Office of Aviation’s 

methodology for identifying coca fields and estimating the amount of 

coca being eradicated through its aerial eradication program. ONDCP 

completed its study in June 2002 and made numerous recommendations to 

improve the estimates developed by CNC and the Office of 

Aviation.[Footnote 14]

As reported in the ONDCP study, CNC compared its analysis of coca 

fields in a predefined area of southern Colombia with the Office of 

Aviation’s analysis of the same area. The results highlighted the 

dramatic differences in the two approaches. Out of 764 coca fields in 

the designated area, CNC and the Office of Aviation differed on the 

identification of 603 of the fields or about 79 percent. The 

discrepancy was largely based on differences in definition of what 

should be counted as a coca field. According to the ONDCP team, the CNC 

definition was “very conservative” and only classified a field as coca 

“when the field is active and contains only coca.” According to the 

team, this likely led to undercounting. The Office of Aviation used a 

“liberal” definition of coca fields that includes coca seedlings and 

mature plants, as well as coca that is damaged or dead. As a result, 

the team concluded that the Office of Aviation tended to overcount 


The ONDCP team also reported that neither CNC nor the Office of 

Aviation had adopted a statistically rigorous accuracy assessment, 

commonly known as an error:

rate, for their respective methodologies. Based on available data, the 

ONDCP team could not determine the statistical accuracy associated with 

either the cultivation or eradication estimates.

Additionally, the ONDCP team reported that the technologies used by CNC 

and the Office of Aviation were insufficient for the purposes they were 

being used. For example, CNC’s technology does not allow it to account 

for image distortions or changes in terrain and the 

atmosphere,[Footnote 15] and the Office of Aviation’s technology does 

not allow it to accurately account for not only coca that may be 

present, but also other vegetation that, according to the ONDCP team, 

should be separately identified.

The ONDCP team made nearly 20 recommendations to improve the estimates 

developed by CNC and the Office of Aviation. Overall, the team 

recommended that CNC and the Office of Aviation:

² agree on definitions of what constitutes a coca field and the various 

types of other vegetation that may be present,

² conduct quantitative accuracy assessments, and:

² improve their respective methodologies to take advantage of state-of-

the-art advancements in the respective technologies used.

According to CNC and Office of Aviation officials, many of the 

recommendations are in the process of being implemented. CNC officials 

told us they plan to implement all of the recommendations pertaining to 

CNC and have contracted with one of the ONDCP team members to help. CNC 

expects to have many of the recommended changes in place for its 2002 

analysis (for release in March 2003). Officials from the Office of 

Aviation said some of the recommendations pertaining to it would 

probably not be fully implemented in the foreseeable future because of 

insufficient funding. For example, upgrading its technology to identify 

more types of vegetation will not be undertaken at this time because of 

the expense involved. A meeting between CNC and Office of Aviation 

officials to discuss recommendations affecting both organizations--

such as coca field definitions--is planned for early 2003.[Footnote 16]

Agency Comments:

The Department of State provided written comments on a draft of this 

report (see appendix). State noted that we provide a useful description 

of the differences and limitations of measuring aspects of illegal drug 

cultivation in Colombia. State also commented that this is an extremely 

important issue that directly affects U.S. drug policies, programs, and 

budgets. It went on to elaborate on some of the limitations associated 

with estimating coca cultivation and production.

In addition, ONDCP, CNC, and Office of Aviation officials provided 

technical comments that we have incorporated into this report, as 


Scope and Methodology:

To determine the purposes of the Colombian coca estimates prepared by 

CNC and the Office of Aviation and the status of the ONDCP team’s 

recommendations, we reviewed relevant documentation and met with 

cognizant officials at ONDCP and CNC in Washington, D.C., and at the 

Office of Aviation headquarters at Patrick Air Force Base, Florida. In 

connection with other work, we also traveled to Colombia and discussed 

the coca cultivation and eradication estimates with the Narcotics 

Affairs Section at the U.S. Embassy in Bogotá.

Our review was conducted from April through December 2002 in accordance 

with generally accepted government auditing standards.

- - - - -:

We are sending copies of this report to appropriate congressional 

committees, the Secretary of State, the Director of Central 

Intelligence, and the Director of ONDCP. We will also make copies 

available to others upon request. In addition, this report will be 

available at no charge on our Web site at

If you or your staff have any questions concerning this report, please 

contact me at (202) 512-4268 or Al Huntington, Assistant Director, at 

(202) 512-4140. Other key contributors to this report were Allen 

Fleener and Ronald Hughes.

Sincerely yours,

Jess T. Ford, Director:

International Affairs and Trade:

Comments From the Department of State:

Signed by Jess T. Ford:



United States Department of State Washington, D. C.	20520:

JAN 6 2003:

Dear Ms. Westin:

We appreciate the opportunity to review your draft report, “DRUG 

CONTROL: Coca Cultivation and Eradication Estimates in Columbia,” GAO-

03-319R, GAO Job Code 320115.

The enclosed Department of State comments are provided for 

incorporation with this letter as an appendix to the final report.

If you have any questions concerning this response, please contact 

Rogers Woolfolk, Aviation Advisor, Office of Aviation, Bureau of 

International Narcotics and Law at (202) 776-8704.


Christopher B. Burnham:

Assistant Secretary and Chief Financial Officer:

Signed by Christopher B. Burnham:


As stated.

cc: GAO/IAT - Al Huntington State/OIG - Mr. Berman State/INL/LP - Mr. 

Thomas Martin:

Ms. Susan S. Westin, Managing Director, International Affairs and 

Trade, U.S. General Accounting Office.

Department of State Comments on GAO Draft Report:

DRUG CONTROL: Coca Cultivation and Eradication Estimates in Colombia 

(GAO-03-319R, GAO Code 320115):

The Department of State considered the GAO report “Drug Control: Coca 

Cultivation and Eradication Estimates in Colombia” a useful evaluation 

of the differences and limitations among the different mechanisms 

measuring aspects of illegal drug cultivation in Colombia. This is an 

extremely important issue for the Department of State, one that 

directly affects US drug policies, programs and budgets. We appreciate 

the opportunity to comment on this report.

The Department of State notes that the annual CNC coca cultivation and 

cocaine potential production estimates are often considered the 

official yearly benchmark for US counter-drug programs. As noted in the 

report, the CNC data collection method does not allow analysis based on 

the condition of the coca plant - whether it is dying because of spray 

or newly replanted following eradication.

The health of the coca plant and whether it has been recently replanted 

are significant distinctions. Eradicated fields that are not replanted 

represent a permanent full production loss. Those sprayed fields that 

are replanted also suffer major yearly production losses. Mature coca 

fields are capable of roughly 4 to 5 harvests a year (depending on type 

of coca plant and local climate). Fields replanted with 1-yr-old 

seedlings can, at best, be harvested at the end of 9 to 12 months - 

producing only about 20 percent of a full harvest during its first 

year. Fields that are reseeded will take up to 2 years to yield their 

first coca leaf harvest. As calculated, the CNC estimates of coca 

cultivation do not reflect any reduction of productivity of coca which 

results from replanting of eradicated fields. This in turn could lead 

to a substantial overestimate of total coca production.

The Colombia spray eradication program is designed to inflict 

economic damage to both the farming and refining segments of the 

industry long enough to force both to dramatically reduce cocaine 

in the medium term and face bankruptcy in the long term. With the vast 

spraying undertaken (nearly 130,000 hectares of coca in 2002 and up to 

hectares planned for 2003) eradication has become the single greatest 
factor in 

our war against Colombian cocaine.

we recognize that both coca farmers and the cocaine industry are able 

and willing to absorb major losses in production for a short period 

(perhaps for as much as 2-3 years), while still keeping up the area 

under cultivation and supply the world market with drugs. Until the 

eradication program operates successfully long enough to exhaust their 

ability to absorb losses and use up product and financial reserves, it 

is likely that there will not be significant reduction to the acreage 

of coca cultivation (which can be replanted almost immediately 

following successful spray eradication).

[End of Section]


[1] The leaves of the coca plant are the raw ingredient of cocaine and 

opium poppy is used to produce heroin. The plants are sprayed from low-

flying airplanes with an herbicide that attacks the root system.

[2] A hectare is 2.47 acres.

[3] CNC’s estimates are presented in its report titled Latin American 

Narcotics Cultivation and Production, Estimates 2001 (Washington, D.C.: 

March 2002).

[4] At about the same time, the government of Colombia’s coca 

cultivation estimate for the same period showed a net decrease of 11 

percent. The Colombian government numbers are from the United Nations’ 

Drug Control Program’s report Colombia: Annual Coca Cultivation Survey 

2001 (Bogotá: March 2002). 

[5] According to CNC, slightly more than 33 percent of the increase was 

the addition of a growing area not previously included. The increase in 

the “traditional” growing areas was 16 percent.

[6] U.S. Embassy, Bogotá cable 2020, March 4, 2002.

[7] CNC officials noted, however, that CNC had concluded that coca 

cultivation in southern Colombia was reduced 22 percent by aerial 

eradication operations that took place the prior year between 

December 19, 2000, and February 5, 2001.

[8] According to Office of Aviation officials, it may take 45 days or 

more for coca plants to show the effects of aerial eradication. Most of 

the imagery CNC analyzed for its 2001 estimate was taken before or less 

than 45 days after the major aerial eradication effort in southern 

Colombia and would not likely have shown the effects of the spraying.

[9] The multi-spectral cameras the Office of Aviation uses allow it to 

examine three different light-band settings.

[10] 22 U.S.C. 2291j. Alternatively, the President may certify that 

vital U.S. national interests require that assistance be provided.

[11] 22 U.S.C. 2291. 

[12] Selected fields are also visually examined either by flying low 

over the field in helicopters or, occasionally, by landing and more 

closely inspecting the plants.

[13] Based on prior experience, the Office of Aviation estimates that 

87 percent of the coca sprayed eventually dies, but the ONDCP team 

questioned this effectiveness factor. 

[14] ONDCP contracted with four experts in imagery and remote sensing. 

For purposes of this report, we refer to them as the ONDCP team. Its 

final report was titled Methodological and Technological Evaluation - 

Assessing Coca Cultivation and Eradication Impact in Colombia (Putumayo 

Region) (Washington, D.C.: June 11, 2002). 

[15] CNC pointed out that the distortions do not present too much of a 

problem when the images are visually interpreted. However, CNC is 

upgrading its technology to correct for these distortions in 2002 as it 

moves toward a digital imaging system.

[16] An October 2002 meeting was canceled because of scheduling