Thursday, 5 June 2014

Biodiversity rules ok - Costa Rican Adventure Part 4

This is too big a topic to write about in such a small space, and I have become distracted reading about the geology and background of Costa Rica, so I'm sorry if this post takes a circuitous route to the subject in hand. It was sparked by an interesting comment that Jim (our guide at La Leona) made; Costa Rica had no dinosaurs. This is because (obvious to anyone with interest in such things but it never occurred to me before) the central american land bridge between the continents was formed a mere 15-20 million years ago by tectonic plate movements and volcanic activity (see here). But the real distraction started when thinking about the current concern with the rate of species extinction caused by human interference. Alongside the normal very gradual process of extinction there have been what are termed the big five 'extinction events' in the course of the existence of our planet. During each of these a huge proportion of the species on the planet died off. I had became curious as to how long this process took. The most recent of these extinctions, which happened 66 million years ago and famously killed off the dinosaurs as well as up to 75% of all plant and animal species, is referred to as the Cretaceous-Paleogene extinction event. It was caused (at least in part, there is of course much debate on the subject) by the impact of an asteroid. This quote comes from the wiki page where it describes the effects of the impact:

"Such an impact would have inhibited photosynthesis by generating a dust cloud that blocked sunlight for a year or less, and by injecting sulphuric acid aerosols into the stratosphere, which would have reduced the sunlight reaching the Earth's surface by 10-20%. It would take at least ten years for those aerosols to dissipate, which would account for the extinction of plants and phytoplankton, and of organisms dependent on them (including predatory animals as well as herbivores). Small creatures whose food chains were based on detritus would have had a reasonable chance of survival. The consequences of reentry of ejecta into the Earth's atmosphere would include a brief (hours long) but intense pulse of infrared radiation, killing exposed organisms. Global firestorms likely resulted from the heat pulse and the fall back to earth of incendiary fragments from the blast. Recent research indicates that the global debris layer deposited by the impact contained enough soot to suggest that the entire terrestrial biosphere had burned." (my emphasis)

Isn't that mind boggling. Everything on the planet burned, and yet here we are. This extinction took place possibly in as little as 10-12 years. But each time evolution stepped in, plants and animals literally rushed to fill the gaps left by species that had gone and a whole new round of change and growth started. 
Doesn't it make human influence seem slightly irrelevant. But don't be fooled. Life can survive these catastrophes ... humans might not. The biodiversity of the planet is important because nature provides us with our food and water.  Nature is the expert at balance, and when we disrupt that balance we tamper with our own survival. As I pointed out in a previous post, strangler figs do not throttle all the trees in the rainforest, but Britain used to be an island entirely covered in forest, but thanks to human destruction nowadays a mere 12% of our land is forested, and even ancient woodland is controlled and managed by people.  It was the most striking thing about walking in the rainforest, that, apart from the cleared path, it was untouched. 

Pretty pictures now. The animals moved around too much, but the plants stayed still. I know pretty much nothing about plants. Mum however is very knowledgable. These are ferns, all photographed within a few feet of each other. Even I could see the variety in the species. Why? They all occupy the same space and the same niche, so why is there so much variety?




I am more of a fungus fan myself, though still know nothing. But some of them are strikingly beautiful.








Size is everything in the rainforest it seems. Things are huge. Trees are huge, leaves are huge, insects are huge. Or they are tiny.
This is the biggest termite nest we saw, it is about as big as me:
Inside the termite nest (and Jim got me to eat a termite ... they don't taste like chicken.)
Mum spotted this, it is the tiniest ants nest. It is about the size of my finger and the ants were like tiny black specks of dirt:
And beetles come in a mind-boggling variety. I didn't get a photo of the fabulous Hercules Beetle that Jim had as a pet and let me hold, or the phosphorescent click beetle that he caught on our night hike. This is a jewel beetle that landed on mum:
And then there were big ones:
and even bigger ones (probably a Longhorn Beetle); this poor thing appeared to have been half eaten, he had a front leg and half an antenna missing and he limped away up the path:
And a very large bee, that made mum walk swiftly away up the path while I followed it to get a photograph:
One of my favourite photos of the holiday. I don't object to the label 'tree-hugger', it implies a certain sentimentality about nature, but I prefer to think of it more as awe.

2 comments:

  1. the variety of life is mind-boggling and most of all in a rainforest. I love all those ferns and fungi....

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  2. Hi Martine - it's fascinating isn't it .. I love the way the earth has changed so much over time .. and how 'things' evolve ... I take an interest in all these aspects and really need to come back and have a thorough read.

    Sounds like you're having a very informative time .. a good subject for the A-Z next year? Cheers Hilary

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