Tuesday, 26 February 2013

Nature's Connections

On the fundamental interconnectedness of all things.

Simple cause and effect is not enough to explain a chaotic world. A single action seldom result in a single reaction. More often, it triggers a chain of reactions, a wave of perturbations through the fabric of reality, like ripples on a pond. Some are obscure, like dropping a small pebble in a big ocean while others stand out like a large rock dropped in a mill pond with long lasting ripples reflecting back from the edge generating complex interference patterns. 

It may sound philosophically abstract but here are two examples of such complex interactions in nature.  The first involves the smallest primate, Madame Berthe's Mouse Lemur and the second involves the largest land mammal, the African Elephant.

Malagasy Miniature

At only 10cm long and weighing 30g, Madagascar's Madame Berthe's Mouse Lemur(microcebus berthae) is the smallest primate.  Despite its diminutive stature, it travels up to five miles a night searching for food.
Although it is an omnivore, it's major food source is the sweet honeydew excretion from a particular plant hopper bug (flatida coccinea) that feeds exclusively on the sap of a particular type of Liana that grows in the island's dry forest[1]. If any part in this network is broken, all subsequent parts will fail too in a linear domino effect.

Madame Berthe's Mouse Lemur, which is categorised as endangered, was first described as a distinct species in the year 2000.  In the fifteen years from 1985 and 2000 approximately half of the forest in which it lives had been cleared for timber or agriculture. In some locations as much 80% of the first has gone and only a few Baobab trees remain. Another fifteen years and this species of mouse lemur could well become extinct.

African Giant

This second example is more intriguing. Conservationists in Scotland know that a large population of deer can have a devastating effect on forests by overgrazing on shrubs and saplings but a study in Kenya has shown that the opposite can also be true. The investigators compared the health of the whistling thorn acacia tree (acacia drepanolobium) with and without large grazing animals such as elephants and giraffes present over a ten year period[2]. Their surprising conclusion was that those with the animals excluded became less healthy and grew slower.  Could the animals breaking off parts of the tree stimulate new growth? Or could they be eating diseased parts?

Further investigation found that ants were responsible. The tree grows hollow thorns and secretes nectar when attacked. This nectar provides an attractive food to a particular species of ant which lives in the hollow thorns and protects the tree from other parasites. When the large mammals were excluded, the trees produced less nectar and the ant colonies declined. This in turn allowed long-horned beetles to colonise the trees, creating cavities and weakening the wood thus the poor health and slower growth.

So as elephants are being slaughtered at a horrendous rate by ivory poachers we should be concerned not only about the elephants but the health of the habitat as a whole and all other plants and creatures that are interrelated.  Large mammals such as elephants are often thought of as an indicator species, a species that flourishes when the habitat is healthy but this shows that they are more than that, they are a fundamental part of that habitat and their success is required for the health of the habitat.

Both of these cases warn us of the consequences of meddling with finely balanced ecosystems where small, seemingly innocuous, actions can have large unintended consequences.  There are many other such relationships and gaining an understanding of them is crucial for us to take a holistic approach to conservation and to prevent further degradation and collapse of ecosystems.

[1] From "Attenborough and The Giant Egg"
[2] Breakdown of an Ant-Plant Mutualism Follows the Loss of Large Herbivores from an African Savanna,
which was brought to my attention by the The Naked Scientist.

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