Especies invasoras: un reto para la conservación de la biodiversidad en Costa Rica

La amenaza de las especies invasoras en Costa Rica, y en el mundo, no se puede pasar por alto. Con mucho más razón ahora que nos encontramos inmersos en la era de la globalización económica y el libre comercio. La Unión Internacional para la Conservación de la Naturaleza (UICN) ha identificado el problema como “la segunda causa de amenaza y extinción de especies, precedida tan sólo por la pérdida de hábitat”. El comercio internacional es sin lugar a dudas una de las principales causas de este problema. Algunas de las peores introducciones de especies invasoras en el mundo han sido producto de las actividades comerciales internaciones e.g. descarga de aguas de lastre, importación de productos agrícolas, madera, plantas ornamentales, animales ornamentales, etc. De hecho, existe clara evidencia de que el problema de las especies invasoras esta incrementándose debido a los patrones del comercio global. Algo alarmante es que no existen listados precisos de las especies invasoras presentes en los países en vías de desarrollo, Costa Rica no es la excepción. Países en vías de desarrollo como Costa Rica deberían empezar a tomar medidas preventivas ¡inmediatamente! Los costos de control y erradicación de estas invasiones biológicas son extremadamente altos.

Sólo en los Estados Unidos se reporta la presencia de unas 50,000 especies exóticas, 4,300 de las cuales se consideran invasoras; desde patógenos que representan un riesgo para la salud pública como el virus del Nilo Occidental (que por cierto, ya se detectó en Costa Rica); y plantas ornamentales como la hiedra o English ivy (Hedera helix) hasta las iguanas verdes y los jabalíes salvajes o cerdos cimarrones como los que existen en la Isla del Coco. Los costos en que se incurre en su control, más los daños que ocasionan, rondan en el orden de los $138 mil millones al año. Como es de esperarse, los costos anuales a nivel global son titánicos: $1,4 billones, según el Convenio sobre La Diversidad Biológica de la Naciones Unidas. En Australia, otro país seriamente infestado con especies invasoras, se estima que el costo de los impactos económicos y ambientales de sólo 11 especies invasoras de vertebrados (incluyendo camellos, gatos ferales, sapos y caballos) es de $720 mil millones al año. Con respecto a “sapos” me refiero a nuestro famoso Sapo grande (Bufo marinus) nativo de Centro y Sur América. Lógicamente, este sapo no representa ningún problema para Costa Rica pero en Australia es una plaga ecológica desagradable.

Todo esto nos indica que un país como Costa Rica no estaría preparado para costear el control y la erradicación de varias especies invasoras bien establecidas dispersándose por todo el país, como ocurre en otros países del mundo. Todo indica que la prevención es nuestra única solución inmediata para evitar posibles daños ecológicos y económicos irreparables. Además, no le convendría al país mortificarse con más problemas ambientales de los que tiene ahora. Aunque no todo sería prevención, porque, efectivamente ya existen varias especies invasoras en el país. Así que los esfuerzos de control y erradicación deben de empezar ahora mismo para evitar una mayor dispersión de estas especies tan perniciosas.

Desafortunadamente, el tema de las especies invasoras es uno de los vacíos en investigación y conocimiento que se tienen en el país, de acuerdo con el Instituto Nacional de Biodiversidad (INBIO). Se han reportado al menos 1,241 especies exóticas, no obstante, no se sabe aún cuántas son invasoras. Las plantas representan el mayor número con 1,092 especies exóticas registradas. Aunque ya se está empezando a hacer algo al respecto. Existen esfuerzos para controlar la Jaragua (Hyparrhenia rufa) un pasto invasor nativo de África, muy común en Guanacaste, en donde coloniza áreas quemadas y produce un excelente combustible para la generación de incendios forestales, una de las peores amenazas para el bosque tropical seco de Costa Rica. El Guineo de jardín (Musa velutina) es una especie invasora importante en las bajuras de la vertiente del Caribe del país. Es un banano de porte pequeño nativo del sureste de Asia que fue introducido como planta ornamental. En la Estación Biológica La Selva en Sarapiquí se ha venido controlando mediante el uso de herbicidas. Cuando trabajé en esa zona del país fui testigo de otro banano con un evidente comportamiento de especie invasora, el Abacá (Musa textilis), en el valle del río Estrella en la provincia de Limón. El Abacá es otro banano nativo de Filipinas, se utilizaba en la construcción de mecates. En el Carmen de Guadalupe en la zona montañosa al este de San José, pude ver el Guineo Piedra (Ensete ventricosum) otra especie de musácea, originaria de Etiopía y que parece ser invasora también.

Quizás el ejemplo más clásico de las invasiones biológicas que aquejan al país son los venados, cabras, ratas y cerdos salvajes en la isla del Coco, uno de los sitios con mayor endemismo en Costa Rica y por ende seriamente amenazado por estas especies. Las tilapias y las truchas son otras especies peligrosas que ya tienen poblaciones establecidas en varios ríos y quebradas de todo el país. Existe evidencia de los impactos de estos peces en las especies nativas de otros países.

Tuve dos avistamientos interesantes en un par de ocasiones, por cierto muy fugaces y confusas, una en una quebrada en Batán, Limón; y otra en el río Sucio en Sarapiquí; donde pude observar lo que estoy casi seguro que se trataba de un plecostomo (Hypostomus plecostomus) una especie común en la acuariofilia. De hecho dos especialistas de La Estación Biológica La Selva en Sarapiquí me comentaron que ellos sospechaban de la presencia de la especie en la zona y que se encontraban buscando evidencia de su presencia, eso fue en el 2008. Existe una especie nativa de plecostomo, también llamado arrisuaca, (Hypostomus panamensis), sin embargo, su distribución natural está restringida a la zona sur del país en la vertiente Pacífica. Con la introducción de la cultura de los pet shops en Costa Rica es de esperarse que los conservacionistas se vayan a llevar algunas sorpresas desagradables como las que se han llevado los conservacionistas norteamericanos, y en un futuro cercano…

De nuevo, la prevención será la mejor iniciativa inmediata para evitar futuros embates por parte de este complejo problema de conservación. La legislación puede ser una herramienta exitosa; Estados Unidos y, recientemente, México han adoptado medidas legales para controlar este problema. Leyes efectivas deberían prevenir y prohibir la introducción de especies invasoras; formular mecanismos para su control y erradicación, implementar acciones para educar a la población, regular las actividades de los sectores económicos responsables de la introducción de especies invasoras, por ejemplo los viveros y el negocio de las mascotas.

Por el momento es necesario iniciar actividades de control y erradicación de estas especies, también implementar sistemas de detección temprana y de respuesta rápida. Cuando se trata de la eliminación de plantas invasoras no existe casi ningún impedimento, pero cuando se trata del control de animales hay que cuidarse de la irracionalidad de los grupos protectores de animales de corte extremista. Estos grupos tienden a mezclar erróneamente consideraciones éticas en asuntos de conservación que requieren razones técnicas y científicas. El problema de las especies invasoras es un problema de origen antrópico, por lo tanto sólo nosotros los seres humanos podemos solucionarlo y para eso muchas veces hay que recurrir al sacrificio de animales. Quizás no sea algo agradable pero este problema NUNCA se va a solucionar por sí solo, hay que intervenir y de manera oportuna y con celeridad.

Tropical passion flowers and passion fruits. by Jorge Bogantes Montero, volunteer

Published in the U.S. Botanic Garden Newsletter "As the Garden Grows", Volume 7, Number 3/ Summer 2009

If a pretty flower or a tropical fruit flavor could transport our minds to the tropics, passion flowers/passion fruits would be some of the chosen ones. When hiking through the tropical rainforest trails of Costa Rica (where I am from), the sighting of a Grape-leaved Passion Flower (Passiflora vitifolia) used to bring a spectacle of exquisiteness which often jumps out of the apparent deep green monotony of these amazing forests. The contrasting splash of bright colors and exotic shapes of the passion flowers are normally a good reason to stop and behold. After pollination, these plants produce the extraordinary passion fruits or granadillas, which are almost all edible though not all the species produce fruits that are palatable enough to be eaten. The edible parts of passion fruits are the arils (the pulp covering the seeds) and the mesocarp (the fleshy wall underneath the peel where the seeds are attached). However, in the commercial species only the aril is edible, since the mesocarp is too crusty and insipid. The sweet/tart freshness of these fruits provides an excellent remedy for hot sunny days, perhaps, anywhere in the world. Even though Passiflora, which is the genus encompassing all the species of passion flowers/passion fruits, are not restricted to the tropics; the most important species are, at least economically speaking. There are more than 500 species of passion flowers of tropical and subtropical origin, of which 90% are native to the Americas. Here are the number of species for three selected countries: 9 in the USA, about 50 in Costa Rica, and, more than 200 species in Brazil. There is at least one local species of passion flower with edible fruits around the DC area, Passiflora incarnata, this species is known as ‘Maypop’.

Some passion flower species are important food crops and ornamentals. In Costa Rica, these plants are widely used in butterfly farming as host plants for the beautiful heliconian butterflies, whose larvae feed on the foliage of these plants. The outstanding beauty of these ‘exotic’ flowers has given them the suggestive name. Although, some people are likely to be surprised when they learn about the actual origin of this common name. Passion flower (or Passiflora in Latin) does not refer to any sort of love lore; but rather has a religious origin. When catholic Spaniards arrived to what today is Latin America, they named it passion flower in reference to the symbols of the passion of Christ. The flowers’ corona -the colorful threadlike filaments set in a circle around the flower’s reproductive organs- represents the crown of thorns said to have been placed on Jesus’s head. The style (female flower part) which is divided into three parts, denotes the three nails; the five stamens (pollen-bearing parts) stand for Christ’s five wounds; and the length of time the flower blooms, usually around three days, corresponds to the time between the crucifixion and the resurrection.

A South American species of passion flower, Passiflora edulis, known as Maracuyá in Spanish or Maracujá in Portuguese, produces the popular passion fruits that are consumed throughout the world. This is the one you are likely to get at most grocery stores, ice cream shops, bars, and restaurants. The fruits can be either purple or yellow colored. The purple fruits originally come from Brazilian populations. This passion fruit has an excellent flavor suitable for many kinds of beverages, smoothies, gelati, and cocktails. When buying these fruits at the supermarket attempting to make your own goodies from scratch, you have to bear in mind that the useful part of the fruit is the aril, namely, the somewhat jelly-textured pulp covering each seed and not the seeds themselves! Blending the seeds excessively with the blender will make your juice taste astringent and give an unappealing color to it. Other species with popular passion fruits are: Giant Granadilla (Passiflora quadrangularis) -which the USBG displays at the Conservatory’s Plant Exploration Room-, Sweet Granadilla (Passiflora ligularis), the Banana Passion Fruit (Passiflora mollissima), and a few other South American species. However, all these species are virtually impossible to find in most grocery stores in the U.S., or at least in the DC area.

Passion flowers are not just pretty edible plants; they also have an important medicinal value, at least in the more traditional herbal medicine. Nearly all the plant parts of some species are considered to be effective to treat diseases related to the central nervous system. The plants are also used to combat gastrointestinal problems, pulmonary problems, among others.

Furthermore, passion flowers are not just meant to feed, delight or heal humans! These plants have coevolved with a plethora of organisms in their native habitats. The ecological relationships between these plants and many animals are rather complex. Therefore, all the unique features of passion flower plants that draw our attention (unusual shapes, pretty colors, good flavors, smells, etc.) are the result of this intricate coevolution. As mentioned above, leaves are eaten by butterfly larvae; the plant’s chemical compounds protect these larvae from predators simply by making them toxic! The flowers are usually pollinated by hummingbirds, bees, butterflies, wasps, and bats; but some species do not need the ‘pollination services’ of these animals since they can self pollinate. Passion flower plants have unique structures known as extrafloral nectaries, these are nectar-producing glands located at the leaf stalks and at the leaves edges. The purpose of the extrafloral nectaries is to attract and benefit predatory insects with yummy treats; usually ants that defend the plant from herbivorous insects. I encourage all the readers to explore and enjoy these amazing flowering plants, not only the tropical species, but also the species native to North America, and, more importantly to preserve them!

Where do corn, vanilla and chili peppers come from? A botanical journey to Mesoamerica. by Jorge Bogantes Montero, volunteer

Published in the U.S. Botanic Garden's Newsletter"As the Garden Grows", Volume 7, Number 2/ Spring 2009

Traditionally Mesoamerica has been considered a cultural region that goes from central Mexico to northwestern Costa Rica, thus including Mexico and most of Central America. More recently, the concept of Mesoamerica has been used by many to denote the region from central Mexico to Panama. The former range mentioned is more often referred to by anthropologists and archeologists where as the latter is being widely used by conservationists and international conservation organizations that operate in the region. Mesoamerica has seen the splendor and demise of some of the most outstanding ancient civilizations in the world, the Mayas and the Aztecs. The region is still the homeland of important indigenous populations with ever-amazing cultures but with deep socio-economic problems as well.

In the Pre-Columbian times agriculture was a very important part of the Mesoamerican culture. Plenty of worldwide economically important plant species were domesticated in this region of the world some thousands of years ago by using original agricultural methods. It is thought that agriculture was much more sophisticated in Pre-Columbian Mesoamerica and the South American Andes than in contemporary Europe. This agricultural development could only be compared to that of China.

Mesoamerica is a splendid land of dazzling active volcanoes, rugged topography, highland plateaus, some of the world’s most complex cave systems, lakes, coastal mangrove forests, the world’s second largest coral reef barrier, vast rainforests, tropical dry forests, pine forests, cloud forests, and 7% of the world’s biodiversity in only 0.5% of the world’s territory! This land has been called home by up to 80 indigenous ethnic groups for millennia. Mexico and Guatemala are currently the countries with the largest indigenous population in the region. Their use of local plants for culinary, medicinal and spiritual purposes is still an important part of their culture.

At least 60 cultivated plants species are native to Mesoamerica making it one of the most important regions of the world in terms of the number of native plants of global or local economic importance. Just take a look at your diet and you’ll see the importance of Mesoamerican plants in your life. The carb boost given by the corn cereal in the morning, the peppers adding spice and good taste to your meals, the delicious refried beans in the burritos, a self-indulgent vanilla ice cream in a hot summer day, the rich dark chocolate as an excellent excuse to strengthen your heart with flavonols, the cotton fabric in your apparel, the vitamin C-rich tomatoes, which are curiously the staple of Italian food! and the oily avocados in your guacamole snacks, just to name a few! All these plants have been harvested for thousands of years; the numerous varieties are the result of complex processes of human selection and horticultural methods that have created plant crops with optimal characteristics. Let’s just put it this way, ancient biotechnology added to modern biotechnology have resulted in the creation of hundreds and thousands of cultivars (races or varieties of plants) per specie.

With a total harvest of up to 300 tonnes only in 2007, the U.S. leads the world’s corn production. Even though corn seeds and its flour are very important nutritional constituents used in a who’s who of food items, corn has also got innovative uses such as biodegradable plastic and as biofuel. Corn (Zea mays) is only known as a cultivated plant there’s no such thing as a wild corn plant since the plant can’t live without human nurturing. The origins of corn are still a hot topic of debate within the scientific community but it is certainly known that it was domesticated somewhere in Mesoamerica. The Popol Vuh, which is basically the Mayan bible, suggests that human flesh and blood were made out of corn. Corn-based tortillas and tamales with all their local versions are a quintessence of the Mesoamerican diet. There are more than 250 types of corn native to Latin America (known as corn “races”) with colors ranging from white and yellow to red and purple, the greatest variety of corn races is found in Mexico and the Andes in South America. The hard and starchy corn types from temperate regions of North America and other parts of the world comprise the bulk of the world’s commercial harvest, but the numerous local corn races in Latin American have remarkable local importance. The modern biotechnological advances have skyrocketed the creation of a legion of corn hybrids and genetically engineered corn organisms.

Peppers and chili peppers (Capsicum spp.) (in Spanish ajíes, chiles or pimientos) were the first spice encountered by Spaniards in the Americas. There are wild populations of peppers growing from the southern U.S. to Colombia but it is thought that the domestication might have occurred in Mexico, according to archeological research findings. There are many pepper varieties and at least four cultivated species with different shapes, sizes and spiciness. Both spicy and non-spicy peppers belong to Capsicum genus. The pungent flavor of chili peppers is given by a chemical compound called capsaicin which has been found to possess anticarcinogenic properties. Peppers also have a high content of vitamin C. The cultivation of peppers expanded rapidly in Europe and Africa when dried peppers imported from Latin America had viable seeds. Chilies were introduced to Asia in the 1500’s and were taken up by the local southern Asian cuisines almost straight away. Peppers are nowadays a significant ingredient in Thai, Sri Lankan, Korean and Indian food; India is the world’s largest producer of chili peppers and the producer of some of the spiciest chili peppers in the world.

Like peppers, tomatoes (Lycopersicon esculentum) are another member of the Nightshade plant family (Solanaceae). There are wild species of tomatoes in the Pacific coast of South America. Nevertheless, there’s no evidence of tomato farming before the arrival of the Spaniards in that region. But, there is evidence of the use of tomato in Mexico before that time. So far, tomatoes have reached a greater economic significance outside of its native range, being an important crop in Europe and the U.S. It has been cultivated in the Mediterranean region since the 1500’s where it easily adapted to the local climatic conditions. When first discovered the Spanish conquistadores found tomatoes similar to the European apple, in Italian they are actually called pomodoro (golden apple).

Mexico has had an evident cultural influence in the modern U.S. culture, particularly when it comes to food. An evidence of that influence is clearly seen by the widespread consumption of beans in the U.S., a quick meal burrito at lunch break or the classical chili con carne says it all! Common beans (Phaseolus vulgaris) are found from Mexico to Argentina, there are hundreds of Common bean cultivars, including black beans, kidney beans, navy beans, pinto beans, and so on. It is thought that beans were first domesticated in Mesoamerica and the Andes some 7,000 years ago. Bean seeds (what we usually eat) have to be cooked or toasted to soften the cotyledons (the two seed parts that form one bean) and to eliminate some toxic compounds. Beans contain both protein (22%) and carbohydrates (60%) some fats and minerals. Couldn’t get any healthier, could it?

Vanilla (Vanilla planifolia) and Cocoa (Theobroma cacao) are both native to and were firstly domesticated in Mesoamerica. For more information on these species the USBG has temporary exhibitions and discovery carts, these are a must-see for anyone who wants to learn lots of fun and interesting facts about this wonderful species.

The Totonac Indians of southern Mexico were the first peoples to discover and use vanilla, quite a culinary accomplishment! They used it in combination with cocoa in beverages. They were the world’s main vanilla producers until the mid-19^th century when the majority of the commercial production switched to the Old World tropics as a result of the discovery of hand pollination techniques. Archeological evidence shows that cocoa was first used in Mesoamerica more than 2,500 years ago by the Olmecs and the Mayans. The Spaniards did not discover cocoa until the 1500’s when it became quite the hype between the European upper classes. The Spanish tried to keep it a secret but they couldn’t make it. By the mid-1600’s chocolate became a sensation across Europe, especially in England and the Netherlands. But it wasn’t until the 19^th century that the modern chocolate bar was invented in Switzerland.

Moreover, another Mesoamerican plant is so utterly important in the world that you wear and sleep on its seed’s fibers, that’s right! Cotton. Cotton is the world’s most essential and commonly used source of fiber for fabric. Even though there are at least four species that produce commercial cotton in the world, the Upland Cotton or Mexican Cotton (Gossypium hirsutum) is the most important species to the world’s cotton production. Cultivation of cotton dates back 5,500 years to Pre-Columbian Mexico. Today, some indigenous ethnic groups in the region still use cotton in their beautiful traditional outfits and handicrafts. A trip to the Mayan Guatemalan highlands is definitely a must-see for ethnic textile lovers! The cotton shrub is considered a tetraploid plant (meaning that it has four sets of chromosomes) but it is quite unknown where and how this genetic modification took place. There are more than 1,000 commercial cotton cultivars used in countries like China, the U.S., Brazil and India which differ in the fiber quality and its resistance to plagues.

Who doesn’t like some tortilla chips with a good guacamole dip? It’s just as Mesoamerican as food can get! Isn’t it? When the Spaniards arrived to Latin America avocados (Persea americana) were used throughout the region from Mexico to Venezuela and Bolivia. It is not clear where its domestication took place originally, although it is thought that it could have occurred in separate places throughout Latin America. However, the oldest clues of avocado use date back 10,000 years according to findings in an archeological site in Mexico. There are three major groups or races of avocados: Mexican, Guatemalan and West Indian. Even so, many of the commercial avocados are hybrids. Avocados are rich in nutritive oils that are easily digested; the older the fruit gets the more oils it develops. Furthermore, the fruit contains proteins, vitamins A and C and the sugar content is rather low. About 95% of the avocados grown in California and 80% of the avocados consumed worldwide are Hass avocados, a cultivar developed and patented by a Californian postman and horticulture amateur Rudolph Hass in the early 1900’s. It is not known what variety of seed produced the original Hass mother tree but it became a more than a billion-dollar business solely in the U.S.!

Even chewing gum comes from Mesoamerica! The latex of the Chicle or Sapodilla trees (Manilkara zapota and Manilkara chicle) was chewed by the Mayans thousands of years ago. The first commercialization of chicle to make the chartbuster chewing gum was done in the late 1800’s by an enterprising New Yorker whose name was Thomas Adams, later on it would become an all time success. The natural gum was largely replaced by synthetic rubber which was more convenient for large-scale producers. Natural chewing gum is currently starting to come back with the new appreciation of organic and fair trade products. Verve Inc. the manufacturers of Glee Gum make chewing gum using natural sapodilla tree-made gum base which they buy from local producers in Central America.

Other contributions of Mesoamerica to the world’s useful plants are allspice (Pimenta dioica), the Tequila agave (Agave tequilana), Amaranth (Amaranthus cruentus and A. hypochondriacus) and squashes (Cucurbita moschata, C. pepo, C. argyrosperma and C. ficifolia). But these are just the most popular ones, there are dozens of other fascinating plant species that have a strictly local use and are rarely known to outsiders. If you want to venture more into the Mesoamerican useful plants, food is always the best start. Go to a Mexican, salvadorean or other Central American grocery store or restaurant and discover how a plethora of plant products and byproducts have been the companion of people and their kitchens since ancient times.