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Ecosystems: life that blossoms

Por: Ana Palma

Tasmania. Photo: anyaka/Flickr

Tasmania. Photo: anyaka/Flickr

When we hear about ecosystems, we think of large biomes, such as tropical forests, deserts, savannas, etc.. But that is not it. Biomes actually gather different ecosystems, grouped up according to the type of vegetation, terrain and climate. In the Pantanal biome, for instance, there are regions with ecosystems similar to those in the Amazon and in the Cerrado.

Moreover, within each ecosystem, there is an amazing number of variations. The várzea forests in the lower Amazon are different from those in the mid-Amazon. Atlantic forests change as we enter it, approach a course of water or climb up a hill!

However, life sprouts everywhere! Living beings are born and die, procreate and feet, collaborate and compete in ecosystems of different sizes. Some are huge such as the sands in a beach, the canopy of a forest or the waters in a lagoon; others are midsize, such as the crater of a volcano and an oasis. But they can be increasingly smaller: the leaves of a bromeliad, the garden in your home, a terrarium or a garbage can. If the sun shines only on one of its sides, the trunk of the tree, for instance, can bear different microecosystems, with different populations and physical characteristics.

Organisms and the environment

What is in ecosystem anyway? Ecosystems are formed by the living beings that inhabit it and interact with each other in a certain area (biocoenosis or biotic factors) and the different physical factors that act upon them.

The physical or abiotic factors are the physical and chemical components that reduce an impact over the living beings on a certain environment. For example, climate, temperature, soil composition, rainfall, etc.. A greater variation in temperature, a longer period of drought, an increase in the salinity of soil or water, all of that can trigger ecological.

Pieter Bruegel, the Elder*

Pieter Bruegel, the Elder*

One example of the influence of abiotic factors took place during the Little Ice Age, during the Modern Age (between the 14th and 19th centuries). During that time, the average global temperature dropped between 1 and 1.5°C. By drastically altering the vegetation and climate of the northern hemisphere, this small variation was decisive for the end of Viking colonies in Greenland and the death of half the population of Iceland and a third of the population in Finland. Glaciers in the Alps expanded destroying farms and villages. Moreover, the Thames, in England, and the rivers and canals in the Netherlands started freezing in the winter, which turned them into skating rinks.

We can observe such effects also in Brazil. The "El Niño," a atmospheric/oceanic phenomenon characterized by an abnormal increase in temperature in the surface water of the Pacific, causes severe droughts in the Northeast of Brazil and greatly increases the risk of forest fires in the Amazon. The expansion of dengue fever and other mosquito-borne diseases can also be mentioned as caused by global warming.

Biotic factors

On the other hand, the term "biotic factors" refer to a set of organisms that live within an ecosystem, the relations they establish between themselves and the impact they cause over the environment. In an ecosystem, the term "population" is used to refer to a set of individuals of a single species, and "community" to refer to the group of populations. Each population occupies the place (habitat) and fulfills a role or function (ecological niche) in the ecosystem.

Examples of biotic factors causing ecological imbalances include the increase or decrease of one population, causing an impact over their preys and/or predators, or the introduction of the new species that competes with on already existing species.

Photo: J.M.Garg/Wikipedia

Photo: J.M.Garg/Wikipedia

A good example of that is the giant African land snail (Achatina fulica). Introduced in Brazil in the 1970s as a substitute for escargot, it ended up released in nature, where it reproduced explosively, since it had no natural predators. Today, it has been competing successfully for space and food with native species, reducing the local biodiversity. Moreover, it destroyed plantations and poses a health risk, since it is a potential transmitter of two important human worm infections: abdominal angiostrongyliasis and eosinophilic meningoencephalitis, as well as animal parasitic diseases.

* Winter landscape with a bird trap, 1601

Consultancy/Technical Review: Vanessa Guimarães/Museu da Vida

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