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Editorial

Ecological management and sustainable development in thehumid tropics of Costa Rica

Bert Kohlmanna,∗, William J. Mitschb, David O. Hansenc

a EARTH University, A.P. 4442-1000, San José, Costa Ricab Wilma H. Schiermeier Olentangy River Wetland Research Park, School of Environment and Natural Resources, The Ohio StateUniversity, 352 W. Dodridge Street, Columbus, OH 43202, USAc College of Food, Agricultural, and Environmental Sciences, The Ohio State University, 2120 Fyffe Road, Columbus, OH 43210, USA

a r t i c l e i n f o

Article history:

Received 12 September 2008

1. Introduction

Costa Rica is an ideal reference point for tropical ecology in theworld. It has abundant majestic wet and dry forests, impen-etrable coastal and inland wetlands, wild rivers, productiveestuaries, fog- and rain-shrouded mountains, and active vol-canic landscapes that support some of the most impressivedense biodiversity found on the planet. Because of its for-tuitous tropical setting, it has also served as an importantlocation for agricultural production, including crops such ascoffee, bananas, pineapples, wood and wood products. Itsincredible ecological systems have also attracted more eco-tourists and adventure travelers per square kilometer than anyother country in the world (22.5 international ecotourists/km2

calculated on data reported by the Costa Rican Tourism Insti-tute (ICT) (Instituto Costarricense de Turismo, 2007). Thecurrent focus on climate change has increased interest in theamount of carbon fluxing through these productive ecologi-cal and agronomic systems as well as the potential impacts ofnew weather patterns on coastal and inland systems.

Results of a collaborative research program between EARTHUniversity in Costa Rica and The Ohio State University in theUSA are presented in this special issue of Ecological Engineer-

∗ Corresponding author.E-mail address: bkohlman@earth.ac.cr (B. Kohlmann).

ing. This research suggests how humans and nature can livein harmony and sustainability in this splendid environment.This is the essence of ecological engineering.

The present special issue arose from the vision and desireof EARTH University’s rector, Dr. José Zaglul, and Ohio StateUniversity (OSU)’s College of Food, Agricultural, and Envi-ronmental Sciences dean, Bobby Moser, to initiate strategiccollaborative research and student and faculty exchange.Assistance in doing so was provided by Congressman DavidHobson, 7th Congressional District, of the US House of Rep-resentatives. In spring 2004, the International Programs inAgriculture Office at OSU solicited proposals from its facultymembers with research experience and expertise on topicsof bio-energy and resource management and conservation inthe tropics. In June of that year, it sponsored a visit by Profes-sors Rattan Lal, Jay Martin, William Mitsch, Roger Williams,and Michael Ellis, and Project Coordinator Richard Fortner,to EARTH University. There they met with Professors EdgarAlvarado, Pedro Bidegaray, Raúl Botero, Marlon Brevé, Car-los Hernández, Bert Kohlmann, Humberto Leblanc, CarlosMontoya, Shuichi Okumoto, Jorge Celso Rodríguez, RicardoRusso, Egbert Spaans, Pánfilo Tabora, Julio Tejada, Marvin Weil,and Jane Yeomans. Together they held a seminar at which

0925-8574/$ – see front matter © 2008 Elsevier B.V. All rights reserved.doi:10.1016/j.ecoleng.2008.09.004

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they presented and discussed possible collaborative topics forresearch. Research collaborations were identified in this pro-cess and the results of this meeting were presented to the U.S.Department of Energy (DOE). DOE supported the research pro-posal presented and agreed to provide partial funding for it.Field research was initiated in 2005.

The 11 papers in this special issue focus on topics relatedto the ecology, agro-ecology and social and economic condi-tions found in the Parismina River watershed, in which EARTHUniversity is located. The research focused on solutions toproblems encountered by communities in the watershed andopportunities for sustainable management of the ecosys-tems there. The problems were initially identified by CarlosHernández, the first EARTH Research Coordinator, and weresummarized in a strategic document entitled “A SystemsApproach to Sustainable Development in Rural Communitiesin the Parismina Watershed, Guácimo, Limón, Costa Rica,”which served as a basic reference for ensuing research.

2. The humid tropics of Costa Rica

Costa Rica is a small country (Fig. 1). It has 51,100 km2 ofland surface, only 0.03% of the Earth surface (Ministerio delAmbiente y Energía, 2000). It lies in the tropics between 8◦2′Nand 11◦13′N; therefore, day length varies only slightly duringthe year. It is bordered on the north by Nicaragua and on thesouth by Panama. It runs in a northwest to southeast axis andis flanked on the west by the Pacific Ocean and on the east bythe Caribbean Sea. The country, divided into seven provinces,is about 259 km at its widest point (east to west) and 119 kmat its narrowest and 464 km along its longest axis. Because nopoint in Costa Rica is more than 130 km from the coast, thecountry’s climate is mostly under maritime influence, espe-cially from easterly trade winds, and is also heavily influenced

Fig. 1 – Costa Rica from space, showing humid Caribbeanside and dry Pacific side. View looking north (fromKohlmann et al., 2002).

Fig. 2 – Mean annual air temperature of Costa Rica (fromKohlmann et al., 2002).

by the Inter-Tropical Convergence Zone (ITCZ) (Hartshorn etal., 1982).

The geography of Costa Rica is exceedingly complex for anarea approximately the size of West Virginia or San BernardinoCounty, California (Savage, 2002). Costa Rica has four dif-ferent mountain ranges: Guanacaste, Tilarán, Central, andTalamanca. The highest peak is Cerro Chirripó (3820 m abovesea level), in the Talamanca Cordillera. Costa Rica is also a priv-ileged country in regard to water resources, due to its tropicalhumid climate (Fig. 2) and related high precipitation (Fig. 3).Most of the country is usually under cloud cover and CostaRicans jokingly call it the “cloud country.”

Costa Rica ranks about 20th among nations of the worldin terms of its biodiversity. Thus, it is not considered to be amegadiverse country, a title enjoyed by only twelve nations.However, what makes Costa Rica special is its species den-sity (number of species per unit area); it is currently rankednumber one in the world in that index (Valerio, 1999; Obando,2002). Costa Rica has 28.2 species of terrestrial vertebrates per1000 km2. By contrast, Ecuador, which has the richest biodi-

Fig. 3 – Mean annual rainfall of Costa Rica (from Kohlmannet al., 2002).

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Fig. 4 – Endemic plant (Araceae, Arecaceae and Bromeliaceae) and dung beetle (Scarabaeinae) species densities in CostaRica.

versity in the world in absolute species numbers, has only9.2 species of vertebrates per 1000 km2 (Valerio, 1999). CostaRica possesses about 4% of the world’s total species diversity,but if the total number of described species is considered, thisnumber increases to 5.4% (Jiménez, 1995). It is also a very richcountry in endemic species (Kohlmann et al., under review,Fig. 4).

This biodiversity has been a major reason for tourists andecotourists to visit the country, and has helped to make eco-tourism the primary source for foreign currency generation.Over the last ten years, ecotourism has surpassed coffee,bananas, and beef productions, which have been the threetraditional major export products of Costa Rica (Damon andVaughan, 1995; Hall et al., 2000; Ambientico, 2001). In 2007,tourism generated US$1895 million, while coffee generatedUS$255, and banana production generated US$674 in for-eign currency (Instituto Costarricense de Turismo (ICT), 2007;Sistema de Indicadores sobre Desarrollo Sostenible, 2008).This signifies an important and rapid change for the economiceconomy (Fig. 5), especially since coffee had been the primaryengine of Costa Rica since the mid 19th century (Hall et al.,2000).

Costa Rica ranks high in the world in terms of its protectedareas. Nearly 23% of Costa Rica’s land area is under some sortof public park system. This figure increases to 28% if privatelyprotected areas are included, and represents one of the high-est national percentages of protected areas in the world. CostaRica may be one of the wettest nations in the world as well,since most of its area receives at least 2500 mm of annualrainfall (Hartshorn et al., 1982).

Fig. 5 – Land use of Costa Rica (from Kohlmann et al., 2002).

3. Costa Rica’s unique culture and history

Costa Rica is a democracy and has no armed forces. Its pop-ulation hovers around 4.5 million. Life expectancy was 76.1years for men and 80.8 years for women in 2005 and the infantmortality rate is 9.52 per 1000 in 2008 (Instituto Nacional deEstadística y Censos (INEC), 2008; Sistema de Indicadores de

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Desarrollo Sostenible, 2008). Its literacy rate was over 95.3% in2000 (INEC, 2008) and its net reproductive rate decreased from2.84 in 1960 to 0.92 in 2006. Costa Rica dedicated 17.3% of theGNP to social expenditure in 2005 (INEC, 2008). Only 4.6% ofthe workforce was unemployed in 2007 and 28% has access tocomputers (INEC, 2008).

Historically, Costa Rica was where Meso-American andSouth-American cultures interfaced with one another. Thefirst group in the country’s northwest were the Chorotega peo-ple, whose primary agricultural crop was maize. Other majorcultural groups along the Caribbean coast and highlands werethe Huetares, Diquis, and Talamancas. Their food staples wereyuca, tubers, and the peach palm.

The colonial period began with the arrival of Columbusto the region in 1502. The first colonial expedition to estab-lish settlements in the north occurred around 1560 underthe leadership of Juan de Cavallón. During this process theIndian cultures were destroyed and lost. According to a recentinterpretation of the era (Gudmundson, 1986), Costa Rica wasoccupied by small communities during the colonial period.Residents of these communities grew subsistence crops on thesurrounding lands. No real urban centers emerged and therewas little exchange among villages. The lack of exploitableminerals and the pattern of small holder development gener-ated a “rural democratic model” that is still very much presentin the modern Costa Rican society. The colonial period was aperiod of sparse European inhabitation, with most communi-ties centered in the isolated central valleys.

Costa Rica became independent in 1824. However, thearrival of coffee from Jamaica in 1808 started a slow but unre-lenting revolution. By 1832, the first exports were shipped toEurope, via English ships through Valparaíso, Chile. By themiddle of the 19th century, Costa Rica was the world’s lead-ing exporter of coffee. Coffee exports helped to create a socialstructure characterized by a coffee baron class and smallholder and labourer classes (Gudmundson, 1986). Coffee wasresponsible for the first major deforestation in the country.The second serious deforestation phase began with the build-ing of the railroad from the central valleys to the Caribbeanport city of Limón in order to facilitate coffee export. Thisconcession was given to Minor Keith, a U.S. citizen, who alsoreceived land from the government, which he used to establishbanana plantations, thus creating the infamous United FruitCompany and the concept of the “banana republic” (Janzen,1983). A third wave of deforestation occurred with the intro-duction of cattle. Spaniards had introduced this activity duringcolonial times. However, starting in the 1950s and intensify-ing towards the end of the century, beef production more thandoubled, most of it supplying the fast food chains of NorthAmerica (Myers, 1981).

Costa Rica has experienced tremendous change during thepast 20 years. Cattle production has substantially declined.Nontraditional exports, like macadamia nuts, tropical flow-ers, and ferns, and electronic chips, have increased. In 1994,the tourist industry surpassed bananas as the major source offoreign exchange. The hotel industry has mushroomed dur-ing the last 15 years, especially along the northern Pacificcoast, bringing new and important environmental problems,like coastal deforestation, pollution, and a direct competitionwith local communities for use of water. Ecotourism in partic-

ular has flourished to the point where Costa Rica is viewed asa world leader in this arena.

The government has been very eager to preserve andexpand the national parks. However, the greatest expansion ofparks has been in the private sector, which has profited from itby creating an important network of private nature preserves.Ecotourism is a new and strong economic driving force in theeconomy and represents hope that development and naturalresource conservation can go hand in hand.

4. Costa Rican ecological and agronomicresearch

Costa Rica has been a haven in tropical biology, ecology, envi-ronment, and agriculture research. A strong institutional basefor research and conservation activity exists, including manyinstitutions that have been working in this field in an efficient,stable, and continuous manner. One of the oldest is the Orga-nization of Tropical Studies (OTS), which operates La SelvaBiological Station under the auspices of a conglomerate ofU.S. universities; the Tropical Science Center (El Centro Cientí-fico Tropical, CCT) with its Monteverde Biological Cloud ForestPreserve, the University of Costa Rica (Universidad de CostaRica, UCR), and the National University (Universidad Nacional,UNA). Among the major related agronomic institutions are theTropical Agriculture Center for Research and Teaching (Cen-tro Agronómico Tropical para la Investigación y Ensenanza,CATIE), located in Turrialba, and EARTH University (Universi-dad EARTH), which is the most recent entry to this sector. Thiscritical mass of research and teaching institutions has createda unique environment for knowledge and learning in CostaRica.

5. EARTH University

EARTH (Escuela de Agricultura de la Región Tropical Húmeda)University was created out of a deep conviction that theenvironmental and social challenges confronting the planetcan be resolved through education that promotes not onlyscience and technology, but also essential human values,leadership, and a commitment to social and environmen-tal service. EARTH dedicates extraordinary effort to buildinga learning community that integrates research and com-munity outreach in the educational process. It has anentrepreneurial focus that includes the production, process-ing, and commercialization of agricultural products. EARTHoffers an undergraduate program in agricultural sciences, witha rational use of natural resources leading to the bache-lor’s degree. EARTH (www.earth.ac.cr, Fig. 6), located in thehumid tropics of Costa Rica, is a private, nonprofit, inter-national university inaugurated in 1990. It focuses on thesustainable development of the humid tropics, a region char-acterized by its biological and social richness, but threatenedby extractive processes and the application of productivesystems poorly suited to the protection of this fragile envi-ronment.

EARTH’s programs focus on the humid tropics, a region thatcontains important ecosystems that are home to a wealth ofbiodiversity. Although the humid tropics only cover 6–7% of

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Fig. 6 – Campus of EARTH University, Costa Rica (from Kohlmann et al., 2002).

the world’s surface, estimates are that the humid tropics arehome to 50–80% of the total number of living species. Dueto the vital importance of this region to the sustainabilityof the entire planet, EARTH has dedicated itself to findingways to learn more about how to responsibly manage thiscomplex ecosystem while conserving its biodiversity. It is ded-icated to halting the destruction of this precious resourcewhile improving the quality of life of its inhabitants and ensur-ing the sustainable use of the region’s natural resources inorder to satisfy the demands of today’s and future genera-tions.

EARTH is committed to alleviation of poverty in the regionthrough the provision of educational opportunities to studentswith scarce economic resources, but with the ability to con-tribute to a more just and prosperous society. For this reason,more than 50% of EARTH students have full scholarships whileanother 30% receive partial scholarships. EARTH is committedto preparing the next generation of leaders who will have thecapacity to rationally manage the resources of the region andconserve its biological diversity. That is why EARTH gives pri-ority to students from the humid tropics, students who oftencome from economically marginalized areas with few educa-tional opportunities.

On a global level, EARTH is becoming a point of referencefor concerns of the humid tropics, such as sustainable agricul-ture, and environmental and agro-business education. EARTHis recognized for its contributions to the development of sus-tainable agricultural practices, rational and creative use ofnatural resources, and above all forming leaders to becomeagents of change who can exert a positive influence on soci-ety.

At EARTH, professors, students, and producers activelyparticipate in applied research projects that focus on find-ing sustainable solutions to production and environmentalchallenges faced by communities in the humid tropics. Theseefforts involve the development of technologies and sus-tainable agro-ecosystems, the appropriate management andconservation of the rural landscape, and the careful utiliza-tion of biodiversity and the development of new products.Themes, such as water use, waste management, alternativeenergy sources, sustainable tropical crop and animal produc-tion, dominate its research programs. Projects vary from theuse of banana waste to produce paper, to the crystalliza-tion of proteins in the search for a cure for Chagas disease.The educational process itself is another important area ofresearch with projects focusing on developing innovativelearning methodologies, curricular integration, student life,educational evaluation, and profiling of incoming and grad-uating students.

In this research effort, EARTH cooperates closely with otherresearch and educational centers in Latin America, NorthAmerica, Europe, Asia, and Africa through programs, such asSustainability, Education, and the Management of Change inthe Tropics (SEMCIT). Other opportunities for collaborationhave been provided by the Chagas Space Program, the Envi-ronmental Program of the United Nations, and the GlobalConsortium of Higher Education and Research in Agricul-ture (GCHERA). Collaboration with The Ohio State University,which is a pre-eminent research institution in the areas ofenvironmental and agricultural research, is typical of this net-working effort. It is this collaboration that has produced theresearch findings presented in this special issue.

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6. Major research collaboration betweenEARTH and The Ohio State University

Research collaboration between EARTH University and TheOhio State University over the past several years has focusedon ecosystem services, conservation, and management andalternative energy sources for the tropics. This research hasinvolved active participation by scientists and staff of bothinstitutions in addition to its graduate and undergraduate stu-dents, including representation at this level from Central StateUniversity in Ohio.

The major projects included in this collaboration havefocused on: the efficacy of constructed wetlands for improv-ing water quality in tropical climates; the role of tropicalwetlands in methane production and carbon sequestration;rural household use of bio-digesters to generate methane gasfor cooking; terrestrial carbon sequestration and soil qual-ity in the tropics; the use of biological resources to controlpests and fungi in the production of bananas and pineap-ples in the humid tropics; small farmer livelihood generationin the context of plantation economies; and the adoption ofagro-ecological technologies by small farmers in the humidtropics. These studies have resulted in a number of jointlyauthored papers, most of which are published in this specialissue. A complete list of published papers and abstracts thathave resulted from this collaboration are included in AppendixA.

To facilitate active and open communication among allcollaborators, annual workshops were held at EARTH Uni-versity, where plans for research for the coming year andthe research activities of the previous year were vetted anddiscussed. Principal investigators from The Ohio State Uni-versity and from EARTH University were involved, as weregraduate students from Ohio State and other affiliated institu-tions. These discussions were extremely important in helpingpartners (a) focus on topics of mutual interest; (b) identifyimportant points of research interface; (c) identify appropri-ate additional field work; and (d) identify additional neededresources to carry out the research. Graduate students wereprovided with opportunities to present their thesis researchand to seek critical input to their project designs as well asfield data collection.

Major projects have been on terrestrial carbon seques-tration and soil quality. Prof. Rattan Lal, OSU, has workedwith Profs. Ricardo Russo and Humberto Leblanc, EARTH, onthis topic. They have involved a number of other person-nel, including Juan José Jiménez and Leslie Caron, OSU, andPaula Chacón, EARTH. Prof. Jay Martin, OSU, worked with RaúlBotero, EARTH, on the development and dissemination of bio-digesters to rural communities in the Parismina watershed.Stephanie Lansing and Melanie Miller, OSU graduate students,conducted much of the field worked and data analysis forthis project. Prof. William Mitsch, OSU, partnered with Profs.Carlos Hernández, Julio Tejada, Bert Kohlmann, and MarlonBrevé at EARTH and with researchers at La Selva (OTS) andPalo Verde Biological Station on the study of rivers and wet-lands in Costa Rica. Amanda Nahlik and Blanca Bernal, OSUgraduate students under Prof. Mitsch, assisted with the datacollection and analyses and are incorporating the research

into three theses/dissertations, one of which is completed(Bernal, 2008). In turn, they were assisted by Bryan Smith, Cen-tral State University, who interned at EARTH University undertheir supervision on several occasions, and by several otherstudents from EARTH and OSU. The wetland research wasco-sponsored by the Wilma H. Schiermeier Olentangy RiverWetland Research Park, The Ohio State University. In April2007 advisory committee members of the Olentangy RiverWetland Research Park, toured the collaborative research sitesat EARTH and heard presentations from several researchersand EARTH administrators.

Profs. Kendra McSweeney and David Hansen, OSU, workedwith Prof. Pedro Bidegaray, EARTH, on the study of small farmlivelihoods and plantation economies. David Lansing, OSUgraduate student, has continued his involvement in CostaRica under a Fulbright grant, focusing on the potential forterrestrial carbon sequestration as a source of income gener-ation for small farmers in the Talamanca indigenous reserve.Melanie Miller continued her work in Costa Rica, focusing onthe adoption and abandonment of environmentally friendlyinnovations. Her work was supervised by Prof. David Hansen,OSU, and Prof. Pedro Bidegaray, EARTH. Profs. Roger Williamsand Michael Ellis, OSU, collaborated with Prof. Edgar Alvarado,EARTH, in a study of biological pest and disease controls inpineapple and banana production. They were assisted in theirresearch by several students at EARTH University, includingDiego Inclán, who also interned with OSU partners at the OhioAgricultural Research and Development Center in Wooster,Ohio.

Collaboration was enhanced through two sabbaticalsundertaken by EARTH University professors at The Ohio StateUniversity. Prof. Raúl Botero spent three months working withProf. Jay Martin on the use of bio-digesters to generate cook-ing fuels. While at OSU, he had the opportunity to review andstudy energy generation systems used by Amish farmers inOhio and to recommend waste-generated bio-digesters as analternative energy source for Amish farming operations. Prof.Edgar Alvarado, EARTH University, spent three months withProfs. Roger Williams and Michael Ellis, on the Ohio Agricul-tural Research and Development Center campus writing upthe results of the field research conducted by them in CostaRica.

7. Research in the special issue

This special issue contains 11 papers that present theresults of research on ecological, agro-ecological, and socialdimensions of sustainable development of Costa Rica, partic-ularly in the Parisima River catchment of the northeasternpart of the country. They are briefly summarized hereunder ecological systems, agro-ecological systems, and socialsystems, recognizing full well that significant cross-overoccurred among the three conceptual areas in almost everypaper.

7.1. Ecological systems

Five papers describe the ecology, carbon dynamics, andsustainable management of stream, wetland, and forest trop-

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Fig. 7 – Construction of boardwalk in La Reserva at EARTHUniversity, Costa Rica (photo by W.J. Mitsch).

ical ecosystems in Costa Rica. Stein et al. (2008) describethe benthic ecology of the Dos Novillos River that flowsthrough the 3300 ha EARTH campus. They investigated twosampling methods for describing the benthic invertebratesin the stream, which is typical of so many mountainstreams as they cascade onto the lower gradient plainsof the Caribbean coastal region of Costa Rica. They foundthat each method differed in the composition of organ-isms collected, but that when the collections were translatedto stream water quality indices, the results were simi-lar.

Mitsch et al. (2008) present the multifaceted researchand teaching program related to the wetlands located onEARTH University’s 3300 ha campus. One large 120-ha wet-land slough on campus, referred to as La Reserva wetland, wasoutfitted with floating boardwalks (Fig. 7) as part of this col-laborative research. These boardwalks enabled researchers tobetter measure the wetland’s hydrology, water quality, green-house gas emissions, and carbon accumulation. Based on fieldmeasurements, an average emission of 45 g-C m−2 year−1 ofmethane and an average sequestration of 257 g-C m−2 year−1,almost six times the emission level, were estimated forthis slow-flowing slough. Results from previously published(Nahlik and Mitsch, 2006) data on four of the treatmentwetlands are also presented. They show that water qualityin these wetlands is improved substantially through wet-land processes and dilution of waters from other parts ofthe campus. More than a decade of undergraduate research

and teaching in all of the wetlands at EARTH Universityis also summarized. Wetlands are integrated into all fouryears of education and about 16 undergraduate theses areconducted on EARTH University wetlands and streams perdecade.

Jiménez et al. (2008a,b) describe soil carbon pools andmeasurement techniques for several ecosystems in managedand secondary forests in Costa Rica. These measurementsare important for documenting ecosystem roles in climatechange. Jiménez et al. (2008a) found that the carbon poolsin the western Costa Rican dry forest biome region rangedfrom about 16 kg m−2 in an unburned sugarcane plantationto 6.6 kg m−2 in floodplain forest and 8.0 kg m−2 in a Curatellasavanna, all to a depth of 50 cm. Because the last two sys-tems represent relatively rare dry tropical forests that aretypical of western Costa Rica before human development, theauthors suggest that care must be taken in the Pacific regionof Costa Rica and Central America in the conversion of theseecosystems to agriculture. Sustainable agricultural systemsneed to be maintained as carbon sinks. In contrast, Jiménezet al. (2008b) examined carbon pools in four secondary trop-ical forests in humid eastern Costa Rica, where precipitationis abundant year-round. Here, carbon pools were higher thanthose in the dry tropical forests of western Costa Rica, rangingfrom 18 to 22 kg m−2 in 50 cm.

Bernal and Mitsch (2008) compare carbon profiles and poolsin five wetlands in Ohio and Costa Rica. They found thattropical wetlands had a lower carbon pool than did temper-ate wetlands in the top 24 cm of soil cores. Isolated forestedwetlands had greater carbon pools than did flow-through wet-lands or slow-flowing sloughs. The soil carbon concentrationlevels in two wetlands in Ohio were compared to the concen-trations of adjacent uplands. That study showed that therewas about ten times more carbon in the wetlands than inthe upland. Carbon pools to 50 cm depth were 9–15 kg m−2

for two of the wetlands in Costa Rica, comparable to orslightly higher that the 50-cm pools found in dry tropicalforests in Costa Rica, but less than that found in humid trop-ical forests to the same depth due to the much lower bulkdensity of the wetland soils as measured by Jiménez et al.(2008a,b).

7.2. Agroecosystems

Three papers in this special issue focus on organic manage-ment of agro-ecosystems (banana and pineapple plantations)and ecological engineering techniques for generating bio-gas for electricity and waste management on small farmsin Costa Rica. Demerutis et al. (2008) investigated the effec-tiveness of organic treatments as a replacement for the useof fungicides for the control of post-harvest crown rot inbananas. Crown rot is the most significant post-harvest dis-ease that affects bananas in shipment. Control of this diseaseis important to Costa Rica, because the country is a majorbanana exporter. Demerutis et al. (2008) found no differencesbetween the use of organic and standard fungicides for treat-ment of crown rot. An organic treatment Biocto6 (a seedextract from citrus) in combination with Verdiol wax is rec-ommended as an environmental alternative to conventionalfungicides.

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The pineapple fruit borer, Strymon megarus, has inflictedsignificant damage on pineapple and other cultivated plantsthroughout Central and South America. Given the rapidincrease in pineapple plantations in ecologically rich CostaRica, concern has arisen about the continued use of conven-tional insecticides. Inclán et al. (2008) describe studies done atEARTH University’s experimental farm, where the use of bio-logical controls was compared with the use of the chemicalinsecticides. The biological agents included three microbes,a botanically derived insecticide and a standard syntheticinsecticide—Sevin. Results showed that, by the second yearof study, one of the biological controls—Bacillus thuringiensis(Bt)—had results similar to the chemical control and it wasactually less expensive.

S. Lansing et al. (2008) describe the design and operation ofbiogas digesters used at EARTH University to treat highly pol-luted swine and dairy wastewater. They found that digestersdecreased wastewater chemical oxygen demand (COD) byalmost 90% and that a significant amount of methane (bio-gas) was produced, which generated a substantial portion ofthe direct electrical requirements of the farms.

7.3. Social systems

All of the ecosystem services and ecological engineeringapproaches are meaningless if they are not applied byhumans. Mitsch (1993) and Mitsch and Jørgensen (2003, 2004)recognized this when they developed the definition of ecologi-cal engineering as the development of sustainable ecosystemsthat have human and ecological value. Three papers in thisspecial issue describe the social context of ecological engi-neering and agronomic practices in the Parismina River Basinin Costa Rica. Miller et al. (2008) reviewed the diffusionof agricultural and “conservation” technologies in society.They conclude that costs of environmental programs oftenfall on individual farmers, while the benefits of these pro-grams accrue to the public at large. The centerpiece of thispaper is a survey of 185 individuals in eight rural com-munities in the vicinity of EARTH University. That surveyfound that while only a few ecotechniques disseminated byEARTH University had been widely adopted, adoption of eco-logical approaches was correlated to recent hosting of anEARTH student. The students and their professors are the bestextension agents for diffusion of ecotechnologies to the pub-lic.

Two papers in this special issue investigate the factors thatlimit and enhance the economic development of this north-eastern part of Costa Rica. D. Lansing et al. (2008) researchedthe extent to which large-scale plantation agriculture allowssmall-scale family farms to survive and even thrive by pro-viding income diversity. They found that employment at aplantation was generally not part of a “livelihood diversifica-tion strategy” for small-scale family farms. They conclude thatlarge-scale agribusiness may be a “poverty trap” in the DosNovillos watershed in eastern Costa Rica, just as others have

shown it to be true in other developing countries. Alvaradoet al. (2008) conducted a qualitative study of three commu-nities in eastern Costa Rica to determine “the weaknessesthat are limiting the development of the competitive capac-ities in the agricultural enterprises throughout the ParisminaRiver Basin.” They found that the most important limita-tions are low organization capacity, limited knowledge offinance management, and low levels of technological inno-vation.

8. Conclusions and future directions

The research findings offered in this special issue are repre-sentative of the types of systematic inquiry that are needed inthe humid tropics to ensure that sustainable practices becomea part of the fabric of life in this region. We strongly rec-ommend more efforts designed to integrate the ecological,physical, chemical, and social issues and recommend designsthat balance the needs of humans and nature. This is theessence of ecological engineering, and its mandate is rapidlybecoming more urgent as human and nature interests con-tinue to collide in the tropics.

The research collaboration between OSU and EARTH Uni-versity, represented by the papers in this special issue ofEcological Engineering, is an ideal model that reflects mutualinterest, true interdisciplinary collaboration, and joint produc-tion over an extended period of time. It involved institutionalcommitments on both sides as well as strong collaborationat the scientist-to-scientist level in the field. As a majorpublic-supported research university, OSU was able to bringconsiderable expertise and research history from diverseparts of the world to the program. As a center of excel-lence in tropical agriculture, with a strong commitment toenvironmental sustainability in the humid tropics, EARTHUniversity was able to bring the necessary human and phys-ical resources and knowledge of the region to the researchenterprise. EARTH University is uniquely positioned to facil-itate this type of research through active engagement ofits faculty, staff, and students. We recommend that thismodel be followed in future international research collabora-tions.

Acknowledgements

We appreciate the support provided by U.S. Departmentof Energy Research Grant DE-FG02-04ER63834 to The OhioState University Research Foundation and to EARTH Uni-versity “Earth University/Ohio State University collabora-tive program on environmental research in the humidtropics.” Carlos Hernández is recognized for his fore-sight in establishing the groundwork for this interna-tional collaboration, Wetland research also supported byWilma H. Schiermeier Olentangy River Wetland ResearchPark.

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Appendix A. Published abstracts, graduate theses, and journal papers that have resulted from thecollaboration between EARTH University and The Ohio State University, 2005–2008

Aguilar, F.X., Botero, R., 2006. Los beneficios económicos totales de la producción de biogás utilizando un biodigestor depolietileno de bajo costo. Tierra Tropical: Sostenibilidad, Ambiente y Sociedad 2(1), 15–25.

Alvarado, E., Demerutis, C., Martínez, A., González, M., 2007. Evaluación de fungicidas biológicos para el controlpostcosecha de la pudrición de corona y pedúnculo en pina (Ananas comosus (L) Meer). Asociación Iberoamericana deTecnología Postcosecha, S.A. 8(1), 17–25.

Alvarado, I.M., Molina, K.M., Bol, E.A., 2008. Determination of the competitiveness linkages through the agriculturalassociative enterprises: the case of the communities on the Parismina River Basin in Costa Rica. Ecological Engineering34, 373–381 (this issue).

Bermúdez, F., Alvarado, E., Tabora, P., Castillo, H., Williams, R.N., Ellis, M., 2006. Evaluation of alternative pesticides for thepineapple borer in Central America. Abstract: 5th National IPM Symposium. April 4–6, 2006. St. Louis, MO.

Bernal, B., 2008. Carbon pools and profiles in wetland soils: the effect of climate and wetland type. M.S. Thesis, School ofEnvironment and Natural Resources, The Ohio State University, Columbus.

Bernal, B., Mitsch, W.J., 2008. A comparison of carbon pools and profiles in wetland soils in Costa Rica and Ohio. EcologicalEngineering 34, 311–323 (this issue).

Blazo, J., Yeomans, J., 2006. Manual de Procedimiento: Manejo y Disposición de Residuos Sépticos. Universidad EARTH,Guácimo, Limón, Costa Rica. 14 pp.

Chacón, P., Leblanc, H.A., Russo, R.O., Under Review. Fijación de carbono en un bosque secundario de la región tropicalhúmeda de Costa Rica. Revista de Agricultura Tropical.

Daqui, N.C., Leblanc, H.A., Russo, R.O., Jiménez, J.J., Under Review. Carbon, nitrates and ammonia in biogenic structures andsoil in a secondary forest in the humid tropics of Costa Rica. Biology and Fertility of Soils.

Daqui, N.C., Leblanc, H.A., Russo, R.O., Jiménez, J.J., Under Review. Distribución espacial de carbono, nitratos y amonio enestructuras biogénicas en un bosque secundario de la región tropical húmeda de Costa Rica. Revista Recursos Naturales.

Demerutis, C., Quirós, L., Martinuz, A., Alvarado, E., Williams, R.N., Ellis, M.A., 2008. Evaluation of an organic treatment forpost-harvest control of crown rot of banana. Ecological Engineering 34, 324-327 (this issue).

Fonseca, G., Alice, F.E., Montero, J., Toruno, H. Leblanc, H., 2008. Acumulación de biomasa y carbono en bosquessecundarios y plantaciones forestales de Vochysia guatemalensis e Hieronyma alchorneoides en el Caribe de Costa Rica.Agroforestería en las Américas 46, 57–64.

Garcés, K., Gutiérrez, R., Kohlmann, B., Yeomans, J., Botero, R., 2006. Caracterización del Sistema de DescontaminaciónProductivo de Aguas Servidas en la Finca Pecuaria Integrada de la Universidad EARTH. I. Las Plantas Acuáticas. TierraTropical: Sostenibilidad, Ambiente y Sociedad 2(2), 129–140.

Garcés, K., Gutiérrez, R., Kohlmann, B., Yeomans, J., Botero, R., 2006. Caracterización del Sistema de DescontaminaciónProductivo de Aguas Servidas en la Finca Pecuaria Integrada de la Universidad EARTH. II. Bioindicadores. Tierra Tropical:Sostenibilidad, Ambiente y Sociedad 2(2), 141–147.

Inclán, D.J., Williams, R.N., Ellis, M.A., Fickle, D.S., McClure, K.B., 2006. The effect of neonicitinoids on the multicoloredAsian lady beetle in grapes. Abstract:Annual Meeting OAS. University of Dayton, April 21–23, 2006.

Inclán, D., Williams, R.N., Ellis, M.A., Fickle, D.S., McClure, K.B., 2006. Managing the multicolored Asian lady beetle ingrapes, 2005: Arthropod Management Tests. http://entsoc.org/pubs/index.html (reviewed).

Inclán, D.J., Alvarado, E., Williams, R.N., 2007. Evaluación de Cuatro Insecticidas Naturales para el Control de Tecla, Strymonmegarus (Godart) (Lepidoptera: Lycaenidae), en el Cultivote Pina. Tierra Tropical 3, 199–210.

Inclán, D.J., Bermúdez, F.J., Alvarado, E., Ellis, M., Williams, R.N., Acosta, N., 2008. Comparison of biological andconventional insecticide treatments for the management of the pineapple fruit borer, Strymon megarus (Lepidoptera:Lycaenidae) in Costa Rica. Ecological Engineering 34, 328–331 (this issue).

Jiménez, J.J., Lal, R., Leblanc, H.A., Russo, R.O., 2007. Soil organic carbon pool under native tree plantations in the Caribbeanlowlands of Costa Rica. Forest Ecology and Management 241,134–144.

Jiménez, J.J., Lal, R., Leblanc, H.A., Russo, R.O., Raut, Y., 2008a. The soil C pool in different agroecosystems derived from thedry tropical forest of Guanacaste, Costa Rica. Ecological Engineering 34, 289–299 (this issue).

Jiménez, J.J., Lal, R., Russo, R.O., Leblanc, H.A., 2008b. The soil organic carbon in particle-size separates under differentregrowth forest stands of north eastern Costa Rica. Ecological Engineering 34, 300–310 (this issue).

Lansing, D., Bidegaray, P., Hansen, D.O., McSweeney, K., 2008. Placing the plantation in smallholder agriculture: evidencefrom Costa Rica. Ecological Engineering 34, 358–372 (this issue).

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Appendix A (Continued )

Lansing, S., 2008. Performance and optimization of low-cost digesters for energy production and treatment of manurewastewater. Ph.D. Dissertation, Department of Food, Agricultural, and Biological Engineering, The Ohio State University,Columbus.

Lansing, S., Martin, J.F., Botero, R.B., 2006. Gas production and water quality analysis of agricultural biodigesters in CostaRica. Abstracts, 6th Annual American Ecological Engineering Society Conference, Berkeley, CA. April 12–14, 2006.

Lansing, S., Martin, J.F., Botero, R.B., 2006. Methane production and water quality improvements in agricultural biodigestersin Costa Rica. American Society of Agricultural and Bio. Eng. Int. Conference Proceedings, Portland, OR. July 9–12, 2006.

Lansing, S., Botero, R., Martin, J., 2007. Small-scale digesters in Costa Rica. BioCycle: advancing composting, OrganicsRecycling and Renewable Energy 48(2), 48–51.

Lansing, S., Botero, R.B., Martin, J.F., Dias Da Silva, E., Kreling, J.C., 2007. Effects of feedstock composition on methaneproduction and wastewater treatment in low-tech anaerobic digesters. Abstracts, 7th Annual American EcologicalEngineering Society Conference, Manhattan, KS. May 23–25, 2007.

Lansing, S., Botero, R.B., Martin, J.F., Dias Da Silva, E., Kreling, J.C., 2007. Optimizing methane production and wastewatertreatment in anaerobic digesters. Abstracts, American Society of Agricultural and Biological Engineers InternationalConference, Minneapolis, MN. June 17–20, 2007.

Lansing, S., Nogueira da Silva, T., Dias da Silva, E.S., Víquez, J., Martínez, H., Botero, R.B., Martin, J.F., 2008. Optimizingmethane production and electricity generation in small-scale agricultural digesters in Costa Rica. Abstracts, 8th AnnualAmerican Ecological Engineering Society Conference, Blacksburg, VA. June 9–14, 2008.

Lansing, S., Botero, R., Martin, J., 2008. Wastewater treatment and biogas quality in small-scale agricultural digesters.Bioresource Technology 99, 5881–5890.

Lansing, S., Víquez, J., Martínez, H., Botero, R., Martin, J., 2008. Ouantifying electricity generation and wastetransformations in a low-cost, plug-flow anaerobic digestion system. Ecological Engineering 34, 332–348 (this issue).

Leblanc, H.A., Russo, R.O., 2007. Carbon sequestration in an oil palm crop system (Elaeis guineensis) in the Caribbeanlowlands of Costa Rica. Abstracts, Florida State Horticultural Society Proceedings, FL.

Leblanc, H.A., Russo, R.O., Cueva, J.J., Subía, E., 2006. Fijación de carbono en palma aceitera en la Región Tropical Húmedade Costa Rica. Tierra Tropical: Sostenibilidad, Ambiente y Sociedad 2 (2), 197–202.

Martinuz, A. 2006, Analysis of alternative technologies for controlling the banana burrowing nematode (Radopholus similisCobb, Thorne): A case study of EARTH University’s Agrocomercial farm. M.S. Thesis, CATIE, Turrialba, Costa Rica. 109 pp.

Miller, M.J., Mariola, M.J., Hansen, D.O., 2008. EARTH to farmers: Extension and the adoption of environmental technologiesin the humid tropics of Costa Rica. Ecological Engineering 34, 349–357 (this issue).

Mitsch, W.J, Nahlik, A.M., Wolski, P., Mfundisi, K.B., Zhang, L., Masamba, W.R.L., Bernal, B., Huntsman-Mapila, P., 2007.Tropical wetlands: Seasons, hydrologic pulsing and biogeochemistry. Abstracts, Society of Wetland Scientists 28thAnnual Meeting, Sacramento, CA.

Mitsch, W.J., Tejada, J.C., Nahlik, A.M., Kohlmann, B., Bernal, B., Hernández, C.E., 2008. Tropical wetlands for climate changeresearch, water quality management and conservation education on a university campus in Costa Rica. EcologicalEngineering 34, 276–288 (this issue).

Montoya, C., Russo, R., 2006. Eco-alfabetización: Talleres Integrados de Educación para Escuelas Primarias. Programa deDesarrollo Comunitario. Universidad EARTH, Guácimo, Limón, Costa Rica. 127 pp.

Montoya, C., Russo, R., 2006. Ecoalfabetización. La Habana, CU. Revista Educación 117 (Enero-Abril), 26–31.Nahlik, A.M., Mitsch, W.J., Lansing, S., Martin, J., 2005. Wetland creation for water quality improvement in Costa Rica.

Abstracts, American Ecological Engineering Society (AEES) 5th Annual Meeting, May 18–19, 2004, Columbus, OH.Nahlik, A.M., Mitsch, W.J., 2006. Tropical treatment wetlands dominated by free floating macrophytes for water quality

improvement in Costa Rica. Ecological Engineering 28, 246–257.Nahlik, A.M., Mitsch, W.J., 2007. Methane emissions from tropical wetlands in Costa Rica. Abstracts, Society of Wetland

Scientists 28th Annual Meeting, Sacramento, CA.Nahlik, A.M., Mitsch, W.J., 2008. The effects of hydrology and climate on methane emissions from freshwater flow-through

wetlands, Abstracts, Society of Wetland Scientists 29th Annual Meeting, Washington, DC.Nimukunda, F., Botero R., Yeomans J., Cortés, G., 2006. Manual para la Descripción y el Mantenimiento del Sistema de

Descontaminación Productiva de las Aguas Residuales Provenientes de las Actividades Pecuarias. Tierra Tropical:Sostenibilidad, Ambiente y Sociedad 2 (1) 19 pp.

Springer, M., Vásquez, D., Castro, A., Kohlmann, B., 2007. Bioindicadores de la calidad del agua. EARTH University.Field-guide, Universidad EARTH, Guácimo, Limón, Costa Rica. 6 pp.

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Appendix A (Continued )

Stein, H., 2005. Investigation of anthropogenic influences on the Río Dos Novillos with the help of benthicmacroinvertebrates for water analyses in Guácimo, province Limón, Costa Rica. M.S. Thesis, Universität Hannover,Germany.

Stein, H., Springer, M., Kohlmann, B., 2008. Comparison of two sampling methods for biomonitoring using aquaticmacroinvertebrates in the Dos Novillos River, Costa Rica. Ecological Engineering 34, 267–275 (this issue).

Williams, R.N., Alvarado, E., Quirós, L., Martinuz, A., de la Cruz, R., Ellis, M.A., McClure, K.B., 2006. Insect pest managementwith treated banana bags. Abstract: Annual Meeting OAS. University of Dayton, April 21–23, 2006.

Williams, R.N., McClure, K.B., 2006. Evaluation of treated banana bags for the control of western flower thrips, 2005:Arthropod Management Tests. http://entsoc.org/pubs/index.html (reviewed).

Williams, R.N., Fickle, D.S., McClure, K.B., Inclán, D., 2006. Chemical evaluations for control of the multicolored Asian ladybeetle (MALB) on grapes, 2005: Arthropod Management Tests. http://entsoc.org/pubs/index.html (reviewed).

Appendix B. University Graduation Theses from EARTH University, 2005–2007, derived from theresearch collaboration project

Alvarado, M.F., 2006. Concentración de carbono y nitrógeno a seis frecuencias de poda en Gliricidia sepium y Erythrina sp.Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Álvarez, N., 2005. Fijación de carbono en la biomasa y en el suelo de especies forestales nativas del trópico húmedo.Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Arévalo, D.M., 2006. Insecticidas naturales y sintéticos impregnados en fundas de polipropileno para proteger racimos debanano. Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Ávila, J.R., 2006. Medición de la escorrentía superficial y la erosión en pina, Ananas comosus (L.) (Farinosae: Bromeliaceae),cultivada usando acolchado plástico, en el cantón de Guácimo, zona Caribe de Costa Rica. Licenciatura IngenieroAgrónomo. Universidad EARTH. Guácimo, CR.

Bettoni, A., Gaxiola, F., 2006. Evaluación de coberturas de papel para producción de pina en el Trópico Húmedo. LicenciaturaIngeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Bermúdez, F.J., 2005. Control de dano por Strymon basilides (Lepidoptera: Lycaenidae) en pina. Licenciatura IngenieroAgrónomo. Universidad EARTH. Guácimo, CR.

Brenes, P.A., Vargas, J. P., 2006. Evaluación y manejo de un sistema silvopastoril de Ischaemun ciliare (ratana) y Erythrina fusca(poró blanco). Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Chacón, P., 2006. Captura de carbono en un bosque secundario de la Región Tropical Húmeda de Costa Rica. LicenciaturaIngeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Cocha, A., Munoz, M., 2005. Análisis de la función de limpieza de las aguas residuales recibidas por los humedales de laUniversidad EARTH, Zona Caribe de Costa Rica. Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Coto, J.E., Maldonado, J.J., 2005. Implementación de un sistema para generar electricidad a partir de biogás en EARTH.Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Cueva, J., Subía, E., 2005. Fijación de Carbono en dos sistemas agrícolas del trópico húmedo de Costa Rica. LicenciaturaIngeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Díaz, G., 2006. Efecto de castración en cerdos sobre rendimiento en canal y palatabilidad de la carne. Licenciatura IngenieroAgrónomo. Universidad EARTH. Guácimo, CR.

Daqui, N.C., 2006. Determinación de carbono (C), amonio (NH4) y nitrato (NO3) en estructuras biogénicas de un bosquesecundario de la zona Caribe de Costa Rica. Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

García, F., Giménez, A., 2005. Efecto de tres sistemas de labranza sobre la calidad del suelo y producción de cultivos.Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

González, M., 2006. Evaluación de fungicidas biológicos para el control en postcosecha de la pudrición de corona y pedúnculoen pina. (Ananas comosus (L.) Merr.). Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

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Appendix b (Continued )

Inclán, D., 2006. Evaluación de cuatro insecticidas naturales para el control de Tecla, Strymon megarus (Lepidoptera:Lycaenidae) en el cultivo de pina. Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Kreling, J., Díaz, E., 2006. Evaluación de la productividad y del efluente de biodigestores suplementados con grasasresiduales. Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Lara, G.O., 2006. Evaluación del efecto del nuevo sistema de tratamiento de lodos sépticos en el funcionamiento delhumedal artificial del relleno sanitario. Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Lazo, O., Morera, H., 2006. Evaluación de los costos de producción y el impacto ambiental del sistema de producción decerdos en pastoreo y un sistema convencional en la FIO. Licenciatura Ingeniero Agrónomo. Universidad EARTH.Guácimo, CR.

Manuin, C.S., 2007. Sobrevivencia y concentración de C y N en forrajeras con diferentes frecuencias de corte. LicenciaturaIngeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Marín, A., Aguilar, H., 2006. Evaluación de la efectividad del sistema de tratamiento de lodos sépticos de la EARTH.Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Martínez, H.M., 2007. Valoración ecológica-económica de los beneficios socioambientales de un biogenerador eléctrico.Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Martínez, E.J., Servián, P.L., 2007. Evaluación de la producción de biogas a partir de excretas humanas en un módulo de lasresidencias estudiantiles de la Universidad EARTH. Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Miranda, J.C., 2006. Evaluación de la calidad natural del agua y su variación espacio temporal en el Humedal Natural “LaReserva”, de la Universidad EARTH, Zona Caribe de Costa Rica. Licenciatura Ingeniero Agrónomo. Universidad EARTH.Guácimo, CR.

Miyashiro, G., Meggs, J.C., 2007. Medición del efecto de la aplicación de EM en la generación de gas metano (CH4) en lossistemas biodigestores a escala. Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Montenegro, J., Zeledón, E., 2006. Efecto de tres sistemas de labranza en la calidad de los suelos y el desarrollo de tressistemas de cultivo, tercer ciclo de observación. Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Nogueira, T., Días, E., 2007. Evaluación de la suplementación de biodigestores con grasas residuales en la universidadEARTH. Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Paredes, R.L., Santín, R., 2006. Dinámica de la calidad del agua y la función de limpieza del humedal artificial “FincaPecuaria Integrada” de la Universidad EARTH, Zona Caribe de Costa Rica. Licenciatura Ingeniero Agrónomo. UniversidadEARTH. Guácimo, CR.

Quezada, M.R., Salas, N., 2006. Generación de energía eléctrica a partir de biogás. Licenciatura Ingeniero Agrónomo.Universidad EARTH. Guácimo, CR.

Quirós, J.D., 2005. Evaluación del plástico como cobertura del suelo en el cultivo de pina orgánica. Licenciatura IngenieroAgrónomo. Universidad EARTH. Guácimo, CR.

Romero, W.A., Echeverría, O.R., 2005. Análisis funcional de los humedales del Laboratorio de Procesamiento de Alimentos(LPA) y Planta de Procesamiento de Papel (PPP): Retención de nutrientes y sedimentos. Licenciatura Ingeniero Agrónomo.Universidad EARTH. Guácimo, CR.

Soto, S., 2007. Digestibilidad y contenido de fibra en forrajes tropicales a distintas edades de corte. Licenciatura IngenieroAgrónomo. Universidad EARTH. Guácimo, CR.

Suárez, E., Vargas, I., 2006. Formulación de capas de permeación restringida para la elaboración de fertilizantes deliberación lenta. Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Vera, A., 2006. Propuesta de capacitación para mejorar la gobernabilidad en los miembros del Concejo de distrito delcantón de Guácimo. Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Víquez, J.A., 2007. Evaluación comercial de la productividad y calidad en la producción de biogas con la adición de grasasen el biodigestor. Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Zafra, J.A., Condori, G., 2007. Efecto continuado de 3 sistemas de labranza sobre calidad de suelos y fisiología de 3 sistemasde cultivos. Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

Zavala, Y., 2006. Concentración de carbono y nitrógeno a seis frecuencias de poda en Morus alba y Tithonia diversifolia.Licenciatura Ingeniero Agrónomo. Universidad EARTH. Guácimo, CR.

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