Class notes about biodiversity topic (Unit 3 IB ESS) where topics like conservation, biodiversity, biological hotspots, the IUCN Red List and action taken by NGOs, IGOs and GOs are covered. Concise with diagrams and images to help visualize explanations. Keywords and examples of threatened/endanger...
unit 1 notes( evs, law of thermodynamics and equilibrium)
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What are biological hotspots?
With so many species listed as endangered and limited resources and time, where do we want to focus
our attention? In order to help with this decision making, in 1988, British environmentalist Norman
Myers, proposed the concept of biological hotspots which was then adopted by Conservation
International. The two key elements to the concept are that these sites must have a high level of
endemic species and also be under threat. Following further analysis and a global review Myers
introduced quantitative thresholds. Conservation International now uses the following two criteria, both
of which must be met for a site to be designated as a biological hotspot:
1. It must have at least 1,500 vascular plants as endemics — which is to say, it must have a high
percentage of plant life found nowhere else on the planet. A hotspot, in other words, is
irreplaceable.
2. It must have 30% or less of its original natural vegetation. In other words, it must be threatened.
Identification of biological hotspots allows conservation efforts to be focused in areas where it can
protect the highest numbers of species. There are 34-35 global biodiversity hotspots, mostly located in
the tropical rainforest. They occupy only 2.3% of Earth’s land area but contain approximately 50% of the
earth’s endemic plant species and 42% of all terrestrial vertebrates (birds, mammals, reptiles and
amphibians).
Figure 1. Location of biological hotspots.
Tropical rainforest biomes
Rainforest biomes cover roughly 6% of the land surface and are the most rich and diverse biomes. The
climate conditions are a result of their location near to the equator, which leads to high levels of
productivity. The largest regions of tropical rainforest are located in the Amazon basin, Congo basin and
Indo-Malay region.
, Climatic conditions of a tropical rainforest:
Insolation levels = high
Temperature = 20-34 C
Rainfall = 200-1,000 cm/year
Figure 3. Location of tropical biomes.
Rainforests contain more than half the world’s plant and animal species. The high level of primary
production supports an array of species. They are also the oldest biomes and have developed into climax
communities with high levels of biodiversity.
As illustrated in the figure below, the rainforest can be divided into distinct vertical zones:
The emergent layer which is the highest layer and consists of trees that extend beyond the
general canopy.
The canopy level that is fairly dense and significantly reduces light penetrating further into the
forest.
The understory layer below the canopy layer consisting of shrub plants and tree saplings.
The forest floor or ground layer, which receives less than 2% of the light, so green plants are
limited in number. Humidity is very high due to the limited air movement and high evaporation
rates in the layer.
Each layer of the rainforest has different environmental conditions and hence contains its own unique
community of species, adding to the overall biodiversity.
The nutrient cycles within the tropical rainforest tend to be short. Nutrient levels in the soil are low as
nutrients are easily leached out by the continual rain. Nutrients are mostly held within the biomass
especially the root mats. Therefore, removal of trees can cause nutrient levels within the ecosystem to
decline rapidly. Tropical rainforests also provide goods and services. Resources for humans include food,
timber and medicines. Services include the absorption of carbon dioxide (carbon sink), production of
oxygen, soil stability and filtration of water. Of course, tropical rainforest are significant for many other
reasons which include intrinsic, cultural, spiritual, religious, aesthetical, education and scientific value.
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