Phytotriades

Transcription

samba music Rio de Janeiro, Brazil. it was here in nineteen ninety two that a hundred and seventy two countries met for the Earth Summit 2 the United Nations Convention on the Environment and Development and it was here that the official agenda for biodiversity conservation was opened for the first time it's not that people weren't conserving species or setting up protected areas but this was the first time that international attention was brought to the topic of biodiversity it was here that the official threefold definition of biodiversity as consisting of species diversity habitat diversity and genetic diversity was first formulated and now twenty years on the crisis in biodiversity is even more severe that was then and the feared sixth mass extinction seems very much underway in today's lesson we look at some of the factors that lead to the loss of diversity with four point two point one we discuss the perceived vulnerability of tropical rainforests and their relative value in contributing to global biodiversity four point two point two we also look at four point two point three to discuss current estimates of the number of species past and present and at the rate of species extinction and we describe in four point two point four and we explain the factors that make species more or less prone to extinction and finally with four point two point five we outline the factors used to determine the Red List conservation status of a species in the four point five billion years (of the planet's existence) the fossil record shows that there have been five major periods when most of the biodiversity on Earth was eliminated the causes of these extinctions are not completely clear but one thing seems fairly certain is that abiotic forces in the environment brought about significant changes in the biotic component that made it very difficult for many species to survive some of these events include massive volcanic eruptions widespread drought though catastrophic is also responsible for significant biodiversity loss there is a powerful body of evidence to suggest that and asteroid from space impacted the Earth sixty five million years ago and ending to age of the dinoosaurs have occurred bringing mass species loss with the rise of humankind massive habitat loss continues habitats are fragmented as human development occurs like this road through a forest populations become isolated from each other gene pools which were once large become smaller and genetic diversity and fitness decline as a result another human activity agriculture transforming biodiverse fields and forests into monoculture the use of pesticides another issue that impact species and leads to loss of biodiversity genetic engineering the science of modifying and manipulating genes to create desirable traits in crops and livestock the danger of being that genetically modified pollen could make its way out into the wild leading to loss of diversity this precious wild diversity could contain genetic material that guards against future outbreaks of pests pollution from industries in the use of fossil fuels poaching leading to this ugly scene where the horn of a rhino is stripped as trawlers drag a fine mesh net across the ocean bottom destroying the abiotic environment and catching unwanted species catching shrimp that are too young all of these are a series of issues that affect the trawling industry and fisheries and have a very significant impact on marine ecosystems the introduction of invasive species like the cane toad-Bufo marinus and its notorious introduction into Australia in the nineteen thirties and forties to control beetle pests in sugar cane fields the toad not only failed to control the beetles but it's poisonous gland threatened a lot of its new predators when it comes to the issue of conservation of biodiversity one biome stands above all others in commanding global attention and concern that biome is the tropical rainforest here we can see the several layers of the forest clearly the tall emergent later at the top the biodiverse canopy the understory and of course the floor of the forest here you can see a good picture of the thin soil and the low amount of organic matter that settles on the force floor due to high rates of productivity the soil remains thin and this soil can become very quickly eroded if forests like these are cleared for agriculture once cleared and the soil becomes exposed and depleted of its nutrients then it's very hard for the rainforest to uncover rainforest though might be very resistant to small changes but once major clearing happens it's very difficult for the forest to recover there are a myriad of number of functions that forests perform from regulating the amount of rainfall that happens in all parts of the globe to providing a place for most of the biodiversity on the planet it's been said that the rainforest is nature's pharmacy with range of plant derivatives providing medicines and cures and economic opportunities that are yet to be discovered the rain forest and in fact any habitat can be compared to the stack of dominoes with the inertia referring to how hard it is to get the dominoes falling over in the case of the rain forest so while they may be hard to change and have high levels of inertia once they are changed and it's not that hard for modern machinery to clear a rainforest with large chunks being cleared by the hour once the forest is cleared the capacity to recover or it's resilience is limited and this presents a serious cause for concern because the rain forest is the home to a wide range of diversity it is because of the range of human factors from logging to genetic engineering that scientists believe that we are currently in the midst of a sixth mass extinction the fossil record which is very clear here at the Grand Canyon provides evidence of five mass extinctions in the past extinctions that may have been brought about by ice ages and asteroid strikes and other unexplained and not fully understood changes in climate but today's sixth mass extinction stands apart from the previous five because all of the previous extinctions resulted from abiotic factors like drought and volcanic eruptions or asteroid strikes something from the earth's abiotic environment or from beyond today's six mass extinction is coming from within the bowels of the biota or the living components of the environment human beings due to their activities are impacting not just other living things but also impacting the abiotic environment the rate at which this is happening this sixth mass extinction is also much faster than the five previous mass extinctions which by studying the stories in the rocks we know happened over very long periods of time today species loss is happening at an increasingly alarming rate and this figure that I have here for ten million species just wild guesss really because the estimate for the number of species that we have living on earth runs anywhere from five million to one hundred million such is the level of uncertainty this is what makes the sixth mass extinction different from the previous five and it's what justifies human concern for the environment because without the living environment the life-support system of the planet at least the system that supports life as we know it and our species is under severe threat and it is for this species centred or anthropocentric reason that biodiversity and it's conservation must occupy centre stage as a global environmental issue species come and species go why is that some species like the american cockroach Periplaneta americana has been able to survive over millions of years why is it that biologists are confident that even if a nuclear war happens.. a catastrophic event that one species that's likely to survive is the cockroach some species are clearly less prone to extinction than others let's go into the Northern Range of Trinidad way up into the mountains a thousand meters above sea level where the clouds kiss the mountain tops here we will find and ultra sensitive species one whose range is limited to just mere square kilometers of the planet earth Phytotriades auratus the golden tree frog is endemic to this tiny island in the Southern Caribbean only found at the tops of the two highest peaks on the island its habitat its survival is dependent upon a very delicate balance of moisture pH air quality and it requires bromeliads in the canopy to lay its eggs and allow its tadpoles to develop with such a high level of sensitivity and specificity it is very unlikely that this highly endangered Golden Tree Frog will survive much longer and it is just one of thousands throughout the tropical rainforest biome of the earth many are still being discovered many are still to be discovered and indeed many that have never been discovered have already because extinct the International Union for the Conservation of Nature classifies the diversity of life according to its Red List status some species are of very little concern others though are critically endangered like the Golden Tree Frog and if we were too take these two extremes golden tree frog and the american cockroach and run them through this checklist we can see why one is of least concern the pest which is the cockroach and the other is critically endangered species sitting on the brink of extinction population size the reduction in population size not very significant in the case of the case of the frog because its population was always very small the numbers of mature individuals if you visit the the mountain tops you would be lucky to find any individuals in your visit the geographic range is extremely limited fragmentation or separation is not even an issue in this case because its range his so narrow habitat is extremely sensitive to changes in the pH of rainfall to pollutants that are in the air the area of occupancy is extremely small even within the actual area of the mountain top the frog itself is confined to the canopy and the young are confined to the aquatic environment harbored within the bromelliads obviously the probability of extinction is extremely high in the case of the tree frog and almost non-existent in the case of the cockroach so this list is what determines whether or not something is classified as critically endangered or not critically endangered think about some other creatures and how they would fit into this list has been closed today and we take-up discussion in the next lesson i would like you to reflect on the importance of rain forests reflect upon our discussion from biomes this discussion and to about constructing a argument to support rainforest conservation an argument that can appeal to the ecocentrics and then an argument that can appeal to anthropocentrics and one that can appeal to technocentrics and we will continue this discussion in the next lesson as we state the arguments for preserving species and habitats in four point three point one