{"id":102297,"date":"2008-10-01T08:09:00","date_gmt":"2008-10-01T08:09:00","guid":{"rendered":"http:\/\/weblogs.madrimasd.org\/\/universo\/archive\/2008\/10\/01\/102297.aspx"},"modified":"2010-01-22T03:49:16","modified_gmt":"2010-01-22T02:49:16","slug":"inundaciones-zonas-humedas-y-cambio-climatico","status":"publish","type":"post","link":"https:\/\/www.madrimasd.org\/blogs\/universo\/2008\/10\/01\/102297","title":{"rendered":"Inundaciones, Zonas H\u00famedas y Cambio clim\u00e1tico"},"content":{"rendered":"

Ya hemos hablado en otros post precedentes sobre los suelos de las zonas h\u00famedas<\/FONT><\/A>, est\u00e9n o  <\/SPAN>no permanentemente sumergidos<\/FONT><\/A> bajo el agua. Tambi\u00e9n escribimos en varias ocasiones acerca de las devastadoras consecuencias de las inundaciones<\/FONT><\/A>. Sin embargo, cuando son estacionales<\/SPAN><\/B>, tambi\u00e9n tienen el efecto ben\u00e9fico<\/SPAN><\/B> de fertilizar con nutrientes y sedimentos, los suelos de los deltas y tramos bajos de los cauces<\/SPAN><\/B>. Sobre ellos se edificaron grandes civilizaciones (como la de Egipto en el Nilo) y vive una considerable parte de la poblaci\u00f3n mundial. Los humedales costeros parecen ser, adem\u00e1s,<\/SPAN><\/B> defensas naturales<\/SPAN><\/B> que almacenan el agua sobrante de las inundaciones r\u00edo abajo o r\u00edo arriba (subida del nivel causado por huracanes y tsunamis<\/SPAN><\/B>). Al mismo tiempo, filtran los contaminantes<\/SPAN><\/B> dejando un agua m\u00e1s limpia. La superficie mundial de estos ecosistemas h\u00famedos ha mermado considerablemente debido a<\/SPAN><\/B> su uso para la agricultura, turismo y piscifactor\u00edas, generando que los territorios aleda\u00f1os sean m\u00e1s vulnerables frente a los desastres<\/SPAN><\/B> naturales comentados. Debe quedar bien claro que el vocablo \u201cdesastre natural\u201d debiera siempre entenderse como<\/SPAN><\/B> perturbaciones de gran magnitud que afectan a los intereses humanos, ya que en muchas regiones del planeta los ecosistemas conviven y son efecto, de sus repercusiones. <\/o:p><\/SPAN><\/P>

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Delta Okawango. Fuente: Eyes of Africa<\/FONT><\/A><\/o:p><\/SPAN><\/P>

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\u00daltimamente, se viene cuestionando si tales efectos ben\u00e9ficos pudieran tener una contrapartida negativa<\/SPAN><\/B>, por cuanto emiten considerables cantidades de metano<\/SPAN><\/B> a la atm\u00f3sfera. Sin embargo<\/SPAN><\/B>, debemos recordar al mismo tiempo que estos ecosistemas secuestran tambi\u00e9n considerables cantidades de carbono<\/SPAN><\/B>. Tal debate se me antoja como un grave error de apreciaci\u00f3n por cuanto, somos la especie humana la que ha incrementado alarmantemente las emisiones de este potente gas de invernadero al aire, mientras cada vez atesoramos menos humedales (y por lo tanto emiten menos a nivel global). \u00bfPorqu\u00e9 \u201ccuestionamos su papel y no el nuestro? Los efectos ben\u00e9ficos mentados, \u201cde ser ciertos\u201d sobrar\u00edan para contrarrestar los presuntamente negativos<\/SPAN><\/B>, si tenemos en cuenta una gran multitud de factores. El 25 de Septiembre de 2008, los boletines de noticias Terradaily y Sciencedaily <\/SPAN><\/B>se hicieron eco de los resultados de un estudio que intentaba analizar el efecto de las inundaciones sobre las emisiones de gases por los humedales<\/SPAN><\/B>. La noticia llevaba por t\u00edtulo<\/SPAN>: <\/SPAN>Flooding Might Help Lower Gas Emission From Wetlands<\/FONT><\/SPAN><\/A><\/SPAN>. <\/SPAN>Es decir, las inundaciones disminuyen las emisiones de metano por los humedales<\/SPAN><\/B>. Personalmente, me pareci\u00f3 de lo m\u00e1s l\u00f3gico. Y sobre este tema vamos ha redactar unas l\u00edneas hoy. <\/o:p><\/SPAN><\/P>

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Delta Okawango. Fuente: Eyes of Africa<\/FONT><\/A><\/o:p><\/SPAN><\/P>

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El agua encharcada y la materia org\u00e1nica que se acumula en los humedales, suele estar poco oxigenada cuando<\/SPAN><\/B> el ecosistema disfruta de una gran actividad biol\u00f3gica que lo consume. Bajo estas condiciones, que generalmente se producen en las estaciones m\u00e1s favorables para la vida), se generan pues ambientes an\u00f3xicos (deficientes en ox\u00edgeno disuelto)<\/SPAN><\/B> que dan lugar a una descomposici\u00f3n anaerobia de la materia org\u00e1nica<\/SPAN><\/B>, siendo esta la que libera el metano a la atm\u00f3sfera<\/SPAN><\/B>. Generalmente, en estos ecosistemas, el nivel de las aguas fluct\u00faa de acuerdo con el caudal de los r\u00edos<\/SPAN><\/B> o fuentes que los alimenten (tambi\u00e9n pueden ser de origen fre\u00e1tico). Cuando estos tienen crecidas el agua vuelve a oxigenarse, reduciendo las emisiones <\/SPAN><\/B>del susodicho gas. Pues bien, los investigadores que firman el estudio que ha dado lugar a la noticia que abajo exponemos en suahili, han emulado estas fluctuaciones de caudal artificialmente, mostrando que las riadas mayores son las que mejor<\/SPAN><\/B> act\u00faan en este sentido. Obviamente, era de esperar que en el verano (del hemisferio norte) incremente la actividad biol\u00f3gica y las condiciones de carencia de ox\u00edgeno<\/SPAN><\/B>. No se trata de ning\u00fan descubrimiento espectacular. A falta de consultar otras fuentes, yo hubiera anticipado algo parecido. Lo mismo podr\u00eda decirse respecto a que los bordes de las lagunas emitan m\u00e1s metano que las aguas m\u00e1s profundas<\/SPAN><\/B>, en donde con toda seguridad, sus sedimentos albergan menos materia org\u00e1nica, biomasa y actividad biol\u00f3gica (la noticia no habla de ello). En cualquier caso, resulta un tanto sorprendente que esta nota de prensa<\/SPAN><\/B> (desconozco si se ha tenido en cuenta en la publicaci\u00f3n cient\u00edfica original) soslaye que si actualmente muchos humedales emiten m\u00e1s metano por no recibir \u201cagua oxigenada\u201d <\/SPAN><\/B>en grandes cantidades, se debe a que los embalses y represas que jalonan los grandes cauces fluviales lo impiden<\/SPAN><\/B>. Se trata de un efecto negativo de estas infraestructuras<\/SPAN><\/B>, no solo sobre las emisiones de los humedales, sino tambi\u00e9n de la fertilizaci\u00f3n que comentamos en el primer p\u00e1rrafo. Si deseamos emular a los ecosistemas deber\u00edamos cambiar el modelo de ingenier\u00eda hidr\u00e1ulica que actualmente desplegamos sobre los sistemas superficiales terrestres. Posiblemente lo m\u00e1s interesante del estudio sean las cifras, pero no la sustancia. <\/o:p><\/SPAN><\/P>

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Humedales e Inundaciones Informaci\u00f3n satelital<\/o:p><\/FONT><\/A><\/SPAN><\/P>

Fuente: Te papa atawbai<\/FONT><\/A><\/SPAN><\/SPAN><\/o:p><\/SPAN><\/P>

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 <\/SPAN>De todos los modos, el estudio viene bien con vistas a enfatizar ciertos aspectos de las inundaciones. Si actualmente hacen tanto da\u00f1o a la humanidad no es por su din\u00e1mica intr\u00ednseca, sino porque<\/SPAN><\/B> generamos infraestructuras e incrementamos la densidad de poblaci\u00f3n en \u00e1reas que naturalmente sufren perturbaciones peri\u00f3dicas frecuentes del tipo de los huracanes, tsunamis, inundaciones, etc. Justamente los humedales parece que ayudan a paliar sus efectos, pero al eliminarlas,<\/SPAN><\/B> los habitantes de estas \u00e1reas podr\u00edan quedar m\u00e1s expuestos a sus devastadores efectos. Anta\u00f1o los nativos que all\u00ed viv\u00edan entend\u00edan mejor las fuerzas de la naturaleza y no osaban intentar burlarlas<\/SPAN><\/B>. Hoy no es as\u00ed y pagamos las consecuencias de nuestra arrogancia.  <\/SPAN>Os dejo ya con la noticia para los amantes de las cifras, no sin antes se\u00f1alar que algunos expertos no tienen tan claros el efecto tamp\u00f3n de los humedales litorales<\/SPAN><\/B>, como ya analizaremos en otros post. .    <\/SPAN><\/o:p><\/SPAN><\/P>

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Juan Jos\u00e9 Ib\u00e1\u00f1ez<\/o:p><\/SPAN><\/P>

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Flooding Might Help Lower Gas Emission From Wetlands<\/FONT><\/SPAN><\/A><\/SPAN><\/o:p><\/SPAN><\/P>

by Staff Writers; <\/SPAN>Columbus<\/SPAN><\/st1:City> <\/SPAN>OH<\/SPAN><\/st1:State><\/st1:place> (SPX) <\/SPAN>Sep 25, 2008<\/SPAN><\/st1:date><\/o:p><\/SPAN><\/P>


River floods and storms that send water surging through swamps and marshes near rivers and coastal areas might cut in half the average greenhouse gas emissions from those affected wetlands<\/SPAN><\/B>, according to recent research at Ohio State University. <\/o:p><\/SPAN><\/P>

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The average levels of methane emissions in the deepest water of the wetlands<\/SPAN><\/B> over the course of the study were 6 pounds of carbon per day in the pulsing year and almost 12 pounds of carbon per day during the steady-flow year A study suggests that pulses of water through wetlands result in lower average emissions of greenhouse gases over the course of the year compared to the emissions from wetlands that receive a steady flow of water<\/SPAN><\/B>.<\/o:p><\/SPAN><\/P>

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The study compared the emission of methane from wetlands under two different conditions, one with a pulsing hydrology system designed to resemble river flooding and one with a steady, low flow of water<\/SPAN><\/B>. The research showed that in areas of deeper water<\/SPAN><\/B> within the wetlands, methane gas fluxes were about twice as high in steady-flow systems than they were in pulsing systems<\/SPAN><\/B>. Methane emissions from edge zones, which are sometimes dry, were less affected by the different types of conditions<\/SPAN><\/B>. Methane is the major component of natural gas and is a greenhouse gas associated with global warming. While the Environmental Protection Agency estimates that human activities are responsible for about 60 percent of methane emissions<\/SPAN><\/B> worldwide, wetlands are among the natural sources<\/SPAN><\/B>. Bacteria that produce methane during the decay of organic material cause wetlands to release the gas into the atmosphere<\/SPAN><\/B>.<\/o:p><\/SPAN><\/P>

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The study by <\/SPAN>Ohio<\/SPAN><\/st1:PlaceName> <\/SPAN>State<\/SPAN><\/st1:PlaceType> <\/SPAN>University<\/SPAN><\/st1:PlaceType><\/st1:place> scientists is part of ongoing research comparing pulsing vs. steady-flow conditions in two experimental wetlands on the <\/SPAN>Columbus<\/SPAN><\/st1:place><\/st1:City> campus. \u00abPulsing refers to a number of different conditions in wetlands – river pulses that happen on a seasonal basis<\/SPAN><\/B>, two-per-day coastal tides, and the rare but huge ones, like hurricanes or tsunamis<\/SPAN><\/B>,\u00bb said William Mitsch, the study’s senior author and  <\/SPAN>(\u2026). \u00abOur point is that the healthiest systems and the ones with the lowest emissions of greenhouse gases are those that have these pulses and that are able to adapt to the pulses<\/SPAN><\/B>.\u00bb The research was published in a recent issue of the journal Wetlands<\/SPAN><\/B>. Often called the \u00abkidneys<\/SPAN><\/B>\u00bb of the environment, wetlands act as buffer zones between land and waterways<\/SPAN><\/B>. They also act as sinks – wetlands filter out chemicals in water that runs off from farm fields, roads, parking lots and other surfaces<\/SPAN><\/B>, and hold on to them for years.<\/o:p><\/SPAN><\/P>

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The study examined methane fluxes over a two-year period during which researchers created two different kinds of conditions<\/SPAN><\/B> in two 2.5-acre experimental wetlands. In 2004, scientists used pumps to deliver monthly pulses to create conditions in the wetlands resembling natural marshes flooded with river water<\/SPAN><\/B>. In 2005, researchers pumped approximately the same amount of water but maintained a constant flow of water through the wetlands to mimic less dynamic hydrologic conditions<\/SPAN><\/B>. In addition to methane emissions, the study also investigated other processes such as denitrification, sedimentation, and aquatic productivity<\/SPAN><\/B>. <\/o:p><\/SPAN><\/P>

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The pulsing hydrology experiment was maintained and methane levels were measured approximately twice monthly over the two study years (\u2026). During both years, more methane was emitted during the summer than during other seasons<\/SPAN><\/B> in all portions of the wetlands, with emissions about four times higher during summer in the edge zones<\/SPAN><\/B>. Consistently wet areas released more gases in the spring than did edge zones under both conditions<\/SPAN><\/B>. <\/o:p><\/SPAN><\/P>

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(\u2026). The emissions were at their highest during the summer of the steady-flow year, when the amount of methane released from the deepest part <\/SPAN><\/B>of the wetlands averaged 18.5 milligrams of carbon per square meter of wetland surface per hour. With these wetlands covering about 5 acres, the emissions amounted to an estimated 20 pounds of carbon per day. That level was twice as high as the summertime methane emissions measured from the deepest area of the wetlands during the year of pulsing conditions<\/SPAN><\/B>. <\/o:p><\/SPAN><\/P>

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The average levels of methane emissions in the deepest water of the wetlands over the course of the study were 6 pounds of carbon per day in the pulsing year and almost 12 pounds of carbon per day during the steady-flow year. The researchers suggested that slightly warmer soil temperatures and less fluctuation in water levels during the steady-flow year created conditions that promoted the production of methane<\/SPAN><\/B>. A simultaneous study of carbon collection in the wetlands showed that the different water conditions had no significant effect on how much carbon was stored by the wetlands<\/SPAN><\/B>. Many experts suggest that the benefits of wetlands’ carbon storage capacity offset any damage resulting from their methane emissions<\/SPAN><\/B>. <\/o:p><\/SPAN><\/P>

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Mitsch noted that pulses from storms not only help dissipate one negative effect of wetlands, but also serve as a reminder of how wetlands function to absorb the surge<\/SPAN><\/B>. \u00abIf we didn’t have salt marshes and mangroves in subtropical and tropical coastal areas of the <\/SPAN>United States<\/SPAN><\/st1:place><\/st1:country-region>, it’s safe to say these current storms would have even more damaging effects,\u00bb he said. \u201cWhen you lose wetlands, you’ve lost a place for floodwater to go<\/SPAN><\/B>,\u00bb Mitsch noted. \u00abMother Nature is better at withstanding these pulses than we are. Whether it’s a flooding river or a hurricane, no matter what those pulses are, if there’s a natural ecosystem to absorb them, then we as humans would be safer<\/SPAN><\/B>.\u00bb <\/o:p><\/SPAN><\/P><\/p>\n","protected":false},"excerpt":{"rendered":"

Ya hemos hablado en otros post precedentes sobre los suelos de las zonas h\u00famedas, est\u00e9n o  no permanentemente sumergidos bajo el agua. Tambi\u00e9n escribimos en varias ocasiones acerca de las devastadoras consecuencias de las inundaciones. Sin embargo, cuando son estacionales, tambi\u00e9n tienen el efecto ben\u00e9fico de fertilizar con nutrientes y sedimentos, los suelos de los deltas y tramos bajos de los cauces. Sobre ellos se edificaron grandes civilizaciones (como la de Egipto en el Nilo) y vive una considerable parte de la poblaci\u00f3n mundial. Los humedales costeros parecen ser, adem\u00e1s, defensas naturales que almacenan el agua sobrante de las inundaciones\u2026<\/p>\n","protected":false},"author":26,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0},"categories":[608,603,594,599,600,615,617,595],"tags":[],"blocksy_meta":{"styles_descriptor":{"styles":{"desktop":"","tablet":"","mobile":""},"google_fonts":[],"version":4}},"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/102297"}],"collection":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/users\/26"}],"replies":[{"embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/comments?post=102297"}],"version-history":[{"count":2,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/102297\/revisions"}],"predecessor-version":[{"id":134759,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/102297\/revisions\/134759"}],"wp:attachment":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/media?parent=102297"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/categories?post=102297"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/tags?post=102297"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}