CALGARY, Alberta, February 9, 2009, Gran Tierra Energy Inc. (NYSE Alternext: GTE; TSX: GTE), a company focused on oil exploration and production in South America, today announced the results of an independent reserve evaluation of the company's reserves by GLJ Petroleum Consultants Ltd. effective December 31, 2008.

Proved Reserves Reported in Accordance with United States Reporting Requirements

The following reserves are reported consistent with United States Securities and Exchange Commission rules.

The following table summarizes Gran Tierra Energy's year-end 2008 working interest reserves and net after royalty reserves (with constant December 31, 2008 oil price and cost). Also shown in the following table are Gran Tierra Energy's net after royalty reserves for year-end 2007 (with constant December 31, 2007 oil price and cost).

Total

Total company Light and Medium Oil (SEC Compliant)			2008 Year-End Gran Tierra Energy Working Interest Reserves	2008 Year-End Gran Tierra Energy NAR Reserves	2007 Year-End Gran Tierra Energy NAR Reserves
Reserves Category			MMBO *	MMBO *	MMBO *
Proved
	Developed Producing		11.053	8.967	3.121
	Developed Nonproducing		1.489	1.299	2.142
	Undeveloped		11.687	8.972	1.155
Total Proved			24.229	19.238	6.418

* MMBO (million barrels of oil).

NAR (net after royalty).

       Proved light and medium oil reserves are 19.238 MMBO NAR at year-end 2008 compared to 6.418 MMBO NAR at year-end 2007, an increase of 200%. In addition to the above proved light and medium oil reserves, Gran Tierra Energy also has year-end 2008 NAR proved gas reserves of approximately 1.2 BCF (billion cubic feet). Gran Tierra Energy had no proved gas reserves at year-end 2007.

Colombia

Gran Tierra Energy's Colombia year-end 2008 working interest and net after royalty reserves are shown in the following table (with constant December 31, 2008 oil price and cost). Also shown in the following table are Gran Tierra Energy's Colombian net after royalty reserves for year-end 2007 (with constant December 31, 2007 oil price and cost).

Colombia Light and Medium Oil (SEC Compliant)			2008 Year-End Gran Tierra Energy Working Interest Reserves	2008 Year-End Gran Tierra Energy NAR Reserves	2007 Year-End Gran Tierra Energy NAR Reserves
Reserves Category			MMBO	MMBO	MMBO
Proved
	Developed Producing		9.752	7.833	2.145
	Developed Nonproducing		1.215	1.060	1.299
	Undeveloped		11.476	8.788	0.939
Total Proved			22.443	17.681	4.383

       The increase in proved reserves in Colombia is mainly associated with the acquisition of Solana Resources Limited and new appraisal drilling in the Costayaco Field.

       In addition to the above proved light and medium oil reserves, Gran Tierra Energy also has year-end 2008 NAR proved gas reserves of approximately 1.2 BCF in Colombia. Gran Tierra Energy had no proved gas reserves in Colombia at year-end 2007.

The Costayaco Field 2008 year-end net after royalty reserves are shown in the following table (with constant December 31, 2008 oil price and cost). Also shown in the following table is a comparison of the Costayaco Field 2008 year-end gross lease reserves (with constant December 31, 2008 oil price and cost) to the gross lease reserves estimated in July 1, 2008 (with constant June 30, 2008 oil price and cost).

Costayaco Light and Medium Oil (SEC Compliant)			2008 Year-End Costayaco Gran Tierra Energy NAR Reserves	2008 Year-End Costayaco Gross Lease Reserves	July 1, 2008 Costayaco Gross Lease Reserves
Reserves Category			MMBO	MMBO	MMBO
Proved
	Developed Producing		6.506	8.172	9.637
Total Proved			15.294	19.649	20.542

Argentina

Gran Tierra Energy's Argentina working interest and net after royalty reserves are shown in the following table (with constant December 31, 2008 oil price and cost). Also shown in the following table is Gran Tierra Energy's Argentina net after royalty reserves for year-end 2007 (with constant December 31, 2007 oil price and cost).

Argentina Light and Medium Oil (SEC Compliant)			2008 Year-End Gran Tierra Energy Working Interest Reserves	2008 Year-End Gran Tierra Energy NAR Reserves	2007 Year-End Gran Tierra Energy NAR Reserves
Reserves Category			MMBO	MMBO	MMBO
Proved
	Developed Producing		1.301	1.134	0.976
	Developed Nonproducing		0.274	0.239	0.843
	Undeveloped		0.211	0.184	0.216
Total Proved			1.786	1.557	2.035

       Gran Tierra Energy had no proved gas reserves in Argentina at year-end 2008 or 2007.

Reserves Reported in Accordance with Canadian Reporting Requirements

The following reserves are compliant with Canadian National Instrument 51-101 (NI 51-101) and the Canadian Oil and Gas Evaluation Handbook (COGEH) (with escalated oil price and costs):

Total

Total company Light and Medium Oil (NI 51-101 compliant)			2008 Year-End Gran Tierra Energy Working Interest Reserves	2008 Year-End Gran Tierra Energy NAR Reserves	2007 Year-End Gran Tierra Energy NAR Reserves
Reserves Category			MMBO *	MMBO *	MMBO *
Proved
	Developed Producing		11.877	9.194	3.095
	Developed Nonproducing		1.526	1.328	2.132
	Undeveloped		11.621	8.289	1.178
Total Proved			25.024	18.811	6.405
Total Probable			12.512	8.676	5.024
Total Proved plus Probable			37.536	27.487	11.429
Total Possible			26.233	18.599	4.863
Total PPP			63.769	46.086	16.292

* MMBO (million barrels of oil).

NAR (net after royalty).

Gran Tierra Energy's year-end 2008 NAR reserves compared to year-end 2007 NAR reserves (compliant with NI 51-101 and COGEH) are as follows:

       Proved light and medium oil reserves are 18.811 MMBO compared to 6.405 MMBO at year-end 2007, an increase of 194%. In addition to the above proved light and medium oil reserves, Gran Tierra Energy also has year-end 2008 NAR proved gas reserves of approximately 1.2 BCF (billion cubic feet). Gran Tierra Energy had no proved gas reserves at year-end 2007.

       Probable light and medium oil reserves are 8.676 MMBO compared to 5.024 MMBO at year-end 2007, an increase of 73%. In addition to the above probable light and medium oil reserves, Gran Tierra Energy also has year-end 2008 NAR probable gas reserves of approximately 1.8 BCF. Gran Tierra Energy had year-end 2007 NAR probable gas reserves of approximately 1.2 BCF.

       Possible light and medium oil reserves are 18.599 MMBO compared to 4.863 MMBO at year-end 2007, an increase of 282%. In addition to the above possible light and medium oil reserves, Gran Tierra Energy also has year-end 2008 NAR possible gas reserves of approximately 16.6 BCF. Gran Tierra Energy had year-end 2007 NAR possible gas reserves of approximately 27.3 BCF.

Colombia

Gran Tierra Energy's year-end 2008 Colombia working interest and net after royalty reserves are shown in the following table (NI 51-101 compliant with escalated oil price and cost). Also shown in the following table are Gran Tierra Energy's Colombian net after royalty reserves for year-end 2007 (NI 51-101 compliant with escalated oil price and cost).

Colombia Light and Medium Oil (NI 51-101 compliant)			2008 Year-End Gran Tierra Energy Working Interest Reserves	2008 Year-End Gran Tierra Energy NAR Reserves	2007 Year-End Gran Tierra Energy NAR Reserves
Reserves Category			MMBO	MMBO	MMBO
Proved
	Developed Producing		10.564	8.050	2.119
	Developed Nonproducing		1.240	1.079	1.290
	Undeveloped		11.414	8.108	0.961
Total Proved			23.218	17.237	4.370
Total Probable			11.401	7.706	3.933
Total Proved plus Probable			34.619	24.943	8.303
Total Possible			23.038	15.806	3.527
Total PPP			57.657	40.749	11.830

       The increases in proved, probable, and possible reserves in Colombia are mainly associated with the acquisition of Solana Resources Limited and new appraisal drilling in the Costayaco Field;

       In addition to the above proved light and medium oil reserves, Gran Tierra Energy also has year-end 2008 NAR proved gas reserves of approximately 1.2 BCF in Colombia. Gran Tierra Energy had no proved gas reserves at year-end 2007 in Colombia;

       In addition to the above probable light and medium oil reserves, Gran Tierra Energy also has year-end 2008 NAR probable gas reserves of approximately 0.7 BCF in Colombia. Gran Tierra Energy had no proved gas reserves at year-end 2007 in Colombia;

       In addition to the above possible light and medium oil reserves, Gran Tierra Energy also has year-end 2008 NAR possible gas reserves of approximately 1.9 BCF in Colombia. Gran Tierra Energy had no possible gas reserves at year-end 2007 in Colombia;

The Costayaco Field 2008 year-end net after royalty reserves are shown in the following table (with escalated oil price and cost). Also shown in the following table is a comparison of the Costayaco Field 2008 year-end gross lease reserves (with escalated oil price and cost) to the gross lease reserves estimated in July 1, 2008 (with escalated oil price and cost).

Costayaco Light and Medium Oil (NI 51-101 compliant)			2008 Year-End Costayaco Gran Tierra Energy NAR Reserves	2008 Year-End Costayaco Gross Lease Reserves	July 1, 2008 Costayaco Gross Lease Reserves
Reserves Category			MMBO	MMBO	MMBO
Proved
	Developed Producing		6.639	8.888	9.637
Total Proved			14.747	20.302	20.382
Total Probable			6.744	10.293	14.528
Total Proved plus Probable			21.491	30.595	34.910
Total Possible			14.757	21.823	26.330
Total PPP			36.248	52.418	61.240

Approximately 1.09 MMBO was produced from July 1, 2008 to December 31, 2008. Taking the production volume into account, there is a small increase in proved reserves along with reductions in probable and possible reserves. The reductions in probable and possible reserves are mainly associated with short well test results from Costayaco-6 in December, 2008, that produced 100% water. Gran Tierra Energy plans to perform further testing at Costayaco-6 with a jet pump in early February 2009 to confirm whether oil is present or not.

The drilling of Costayaco-7 is scheduled to commence in February, 2009. Costayaco-7 will be located with the intent of converting probable and possible reserves at the north end of the field into proved reserves. Costayaco-8 is scheduled to be drilled after Costayaco-7. Costayaco-8 will be located with the intent of converting probable and possible reserves at the south end of the field into proved reserves. These two wells are intended to add significant production capacity and contribute to Gran Tierra Energy's expected 2009 exit rate of 19,000 barrels of oil/day (BOPD) net after royalty from Colombia.

Argentina

Gran Tierra Energy's Argentina year-end 2008 working interest and net after royalty reserves are shown in the following table (NI 51-101 compliant with escalated oil price and cost). Also shown in the following table is Gran Tierra Energy's Argentina net after royalty reserves for year-end 2007 (NI 51-101 compliant with escalated oil price and cost).

Argentina Light and Medium Oil (NI 51-101 compliant)			2008 Year-End Gran Tierra Energy Working Interest Reserves	2008 Year-End Gran Tierra Energy NAR Reserves	2007 Year-End Gran Tierra Energy NAR Reserves
Reserves Category			MMBO	MMBO	MMBO
Proved
	Developed Producing		1.313	1.144	0.976
	Developed Ponproducing		0.286	0.249	0.842
	Undeveloped		0.207	0.181	0.217
Total Proved			1.806	1.574	2.035
Total Probable			1.111	0.970	1.091
Total Proved plus Probable			2.917	2.544	3.126
Total Possible			3.195	2.793	1.336
Total PPP			6.112	5.337	4.462

       The additions in probable and possible reserves associated with the Proa-1 oil discovery made in 2008 is offset by the write down of reserves at La Reina Field and Nacatimbay Field;

       Gran Tierra Energy had no proved gas reserves in Argentina at year-end 2008 or year-end 2007;

       In addition to the above probable light and medium oil reserves, Gran Tierra Energy also has year-end 2008 NAR probable gas reserves of approximately 1.2 BCF in Argentina. Gran Tierra Energy had year-end 2007 NAR probable gas reserves of approximately 1.2 BCF;

       In addition to the above possible light and medium oil reserves, Gran Tierra Energy also has year-end 2008 NAR possible gas reserves of approximately 14.7 BCF in Argentina. Gran Tierra Energy had year-end 2007 NAR possible gas reserves of approximately 27.3 BCF.

Current Production

Gran Tierra Energy is currently producing approximately 12,000 BOPD net after royalty. About 11,000 BOPD net after royalty production is from Colombia and approximately 1,000 BOPD net after royalty production is from Argentina.

With the spare production capacity available from existing wells, Gran Tierra Energy plans to increase its net after royalty production in Colombia from 11,000 BOPD to 14,000 BOPD in the first quarter of 2009. This rate is expected to be maintained until the third quarter of 2009. With the planned development drilling in Costayaco and Juanambu, Gran Tierra Energy's net after royalty production in Colombia is expected to increase to 19,000 BOPD in the third quarter of 2009. This rate is expected to remain relatively constant throughout the remainder of 2009.

Gran Tierra Energy's net after royalty production rate for Argentina is expected to remain constant at approximately 1,000 BOPD throughout 2009.

Dana Coffield, President and CEO commented "2008 has proven to be another outstanding year in the growth of Gran Tierra Energy's reserve base, fueled in large part by our acquisition of Solana. The tripling of the company's proved reserves during the year provides a strong foundation for growth in 2009. The development drilling program scheduled for 2009 is expected to continue adding to our production growth, and should convert more of the company's probable and possible reserves to the proved category. We continue to expect attaining net after royalty production of 15,000 BOPD in the first quarter, and 20,000 BOPD in the third quarter, of this year. This activity, in addition to our planned 2009 exploration program, is expected to be funded out of available cash and cashflow from operations, allowing the company to remain debt free."

About Gran Tierra Energy Inc.

Gran Tierra Energy Inc. is an international oil and gas exploration and production company operating in South America, headquartered in Calgary, Canada, incorporated in the United States, and trading on the NYSE Alternext (GTE) and the Toronto Stock Exchange (GTE). The company holds interests in producing and prospective properties in Colombia, Argentina, and Peru. The company has a strategy that focuses on growing a portfolio of producing properties, plus production enhancement and exploration opportunities to provide a base for future growth. Additional information concerning Gran Tierra Energy is available at www.grantierra.com. Investor inquiries may be directed to [email protected] or 1-800-916-GTRE (4873).

Cautionary Statement

Possible reserves are those additional reserves that are less certain to be recovered than probable reserves. There is a 10% probability that the quantities actually recovered will equal or exceed the sum of proved plus probable plus possible reserves. The estimate of reserves for individual properties may not reflect the same confidence level as estimates of reserves for all properties, due to the effects of aggregation.

Forward Looking Statements

The statements in this news release regarding Gran Tierra Energy's timing, plans and expectations for testing, drilling, production, reserve growth, funding of operations, are forward looking information, forward looking statements or financial outlooks (collectively, "forward-looking statements") under the meaning of applicable securities laws, including Canadian Securities Administrators' National Instrument 51-102 Continuous Disclosure Obligations and the United States Private Securities Litigation Reform Act of 1995. These forward-looking statements are subject to risks, uncertainties and other factors that could cause actual results or outcomes to differ materially from those contemplated by the forward-looking statements. Although, Gran Tierra Energy believes that the assumptions underlying, and expectations reflected in, these forward-looking statements are reasonable, it can give no assurance that these assumptions and expectations will prove to be correct. Important factors that could cause the results or outcomes discussed herein to differ materially from those indicated by these forward-looking statements, include, among other things: Gran Tierra Energy's operations are located in South America, and unexpected problems can arise due to guerilla activity, technical difficulties, operational difficulties and geographic, political and weather conditions which can impact the production, transport or sale of its products. Further information on potential factors that could affect Gran Tierra Energy are included in risks detailed from time to time in Gran Tierra Energy's Securities and Exchange Commission filings, including, without limitation, under the caption "Item 1A – Risk Factors" in Part II of Gran Tierra Energy's Quarterly Report on Form 10-Q, filed with the Securities and Exchange Commission on November 6, 2008. These filings are available on a Web site maintained by the Securities and Exchange Commission at http://www.sec.gov and on SEDAR at http://www.sedar.com. The forward-looking statements contained herein are made as at the date of this press release. Gran Tierra Energy does not undertake an obligation to update forward-looking or other statements in this release except as may be required by law. Gran Tierra Energy's forward-looking statements are expressly qualified in their entirety by this cautionary statement.