3.1E Biodiversity hotspots (HL) Notes

1. Biodiversity is not evenly distributed across the planet, certain areas, known as biodiversity hotspots, contain an exceptionally high proportion of species, many of which are rare, endemic, and endangered.
2. These regions are often characterized by high species richness and ecological significance, making them critical for global conservation efforts.
3. Many of these hotspots are located in tropical biomes, where the conditions are ideal for supporting a diverse range of life forms.

Factors Influencing Uneven Biodiversity Distribution

1. Climate Stability: Consistent temperature and rainfall promote species survival and speciation.
2. Primary Productivity: Areas with high photosynthetic rates (like rainforests and coral reefs) sustain complex food webs.
3. Habitat Complexity: Diverse microhabitats allow multiple species to occupy different ecological niches.
4. Evolutionary Time: Regions undisturbed by ice ages or major extinctions have had longer periods for diversification.
5. Isolation: Geographic isolation (e.g., islands or mountain ranges) promotes endemism and unique species evolution.

Global Biodiversity Hotspots

1. There are 36 officially recognized biodiversity hotspots worldwide (as defined by Conservation International).
2. Together, they cover less than 3% of Earth’s land surface but hold over half of all plant species and about 40% of terrestrial vertebrates.
3. Major global hotspots are:
   1. Madagascar and the Indian Ocean Islands: Over 90% of species are endemic; severe deforestation threatens forests.

1. The Western Ghats and Sri Lanka: One of the most species-rich tropical forests in Asia; home to thousands of endemic amphibians and plants.

1. The Indo-Burma Region: Includes Vietnam, Cambodia, Laos, and Myanmar; under pressure from agriculture and urban expansion.

1. Mesoamerica: Spanning Central America and southern Mexico; houses unique rainforest ecosystems.

1. The Caribbean Islands: High endemism but heavily affected by deforestation and hurricanes.

1. The California Floristic Province: A temperate hotspot with numerous endemic plant species, now facing urban and agricultural expansion.

Tropical Biomes as Biodiversity Hotspots

1. Most biodiversity hotspots lie between 15°N and 15°S latitude, within tropical zones.
2. Tropical biomes, rainforests, mangroves, coral reefs, support the highest global species richness.
3. Factors such as constant sunlight, abundant rainfall, and stable temperatures foster:
   1. Continuous plant productivity
   2. High mutation and speciation rates
   3. Complex ecological interactions
4. These include:
   1. Tropical rainforests: Amazon Basin, Congo Basin, Southeast Asia
   2. Tropical coral reefs: Indo-Pacific and Caribbean regions
   3. Tropical dry forests and savannas: Mesoamerica, Cerrado, and Madagascar

Importance of Protecting Biodiversity Hotspots

Conservation Priority

1. Because hotspots contain a large proportion of Earth’s species, protecting them is essential to preserving global biodiversity.
2. Hotspots are also critical for ecosystem services, such as carbon storage, water filtration, and pollination, which support human livelihoods.

Threats to Hotspots

1. Deforestation and land use change are major threats to tropical biodiversity hotspots.
2. Climate change further exacerbates these threats, causing habitat loss and disrupting species’ ability to adapt.