Lecture 2: Human Impact

1. Lecture 2: Human Impact 4 Major Activities that Threaten Biodiversity • 1)Habitat Destruction • 2)Introduced Species • 3)Overexploitation • 4)Disruption of Interaction Networks

2. 1)Habitat Alterations Selective Logging Edge Effects 2)Habitat Fragmentation 3) Clear Cutting 1: Habitat Destruction Includes:

3. Effects of Habitat Destruction: • 1) Selective logging causes gaps in the canopy thus causing an edge effect. • The edges slowly degrade do to wind, invasion of species, and increased sunlight. Degradation of edges can lead to habitat fragmentation. • Some species may become more susceptible to predation because of decreased protection from the forest • 2) Habitat fragmentation cuts species off from larger populations thus causing inability to support viable populations. • 3) Clear cutting for agriculture and pastures. • Because Tropical Rainforest soil is low in nutrient quality approximately 10x more land is needed for grazing animals and the previously cleared ag land is abandoned to clear nearby forest to further grow crops. • Millions of hectares of Brazilian Amazon Rainforest are destroyed every year due to human set fires for agriculture use and by ranchers.

4. Habitat Destruction Disrupts Chemical Cycles of Ecosystems • Nutrient exhaustion in the tropics due to clear-cutting effects the Nitrogen Cycle • This causes an increase in the decomposition rate of organic matter • Slash and Burn practices of forests causes greater releases of nitrogen oxides which contribute to atmospheric warming. • Excess nitrogen and runoff contaminate freshwater and marine ecosystems. • Deforestation leads to a rise in CO2 levels

5. Runoff of sediments, fertilizers, and pollutants due to changes in the nitrogen cycle, agriculture, and tourism increasing development along the coasts Pollutants directly block the light thus killing the corals Pollutants also clog polyps on the corals so the corals cannon perform necessary life functions such as gaining food and oxygen An increase in nutrients can also lead to an increase growth of algae, which results in the death of corals Land Behavior Affects the Oceans Too Pictured Below: Damaged Coral

6. Human Activities lead to Rising Atmospheric CO2 • A rise in CO2causes the greenhouse gas effect where heat is trapped, thus warming the planet. • Warming of the atmosphere causes a warming of ocean temperatures • Warming ocean temperatures cause coral bleaching a phenomenon that turns corals white due to the expulsion of zooxanthella (organisms that provide up to 90% of energy to corals) which in turn leads to coral death • A rise in temp will melt the polar ice caps, rising the current sea level.

7. What Habitat Destruction and Human Impact Means for the Coral Reefs Human Impact directly and indirectly effects the coral reefs. It causes the corals inability to recover quickly, a reduction in growth, and reef mortality.

8. Invasive or exotic species are species that humans move (intentionally or unintentionally) from the species native habitat to a new geographic region Introduced species can disrupt the geographic region they were introduced to causing a disruption of “interaction networks”. 2: Introduced Species • Above: Zebra Mussel, an invasive species introduced to North America via ballast water

9. Humans overharvesting plants and animals Commonly valuable wood or trees are overexploited leading to extinction of tree species Tree exploitation can cause edge effects due to the trees extraction. This is caused because the extracted tree is generally large in comparison to surrounding trees and roads need to be cut to remove the tree. (similar with selective logging) 3: Overexploitation

10. Overexploitation of Terrestrial Animals • Hunting is a problem for many endangered large predators due to their trophy value • Primates are exploited for bushmeat for subsistence/ protein for local populations • Species with restricted habitats or island inhabitants are extremely vulnerable • Example: Lemurs on Madagascar

11. Overexploitation of Marine Life: • Blast Fishing: Indiscriminately kills all marine life, including coral reefs and unknowingly endangered aquatic species • Trawl Nets: the use of trawl nets by fishermen damage coral reefs and sponges due to the weighted net being dragged along the ocean floor. Also, sea turtles are commonly killed as a result of being trapped in the net.

12. 4: Disruption of “Interaction Networks” • Ecosystems depend on species interactions • Disruptions such as habitat destruction and fragmentation cause species to move into new niches possibly displacing previous inhabitants • Example: The decline of Howler monkeys with the increase of Muriquis in Brazil’s Atlantic Forest • The extinction of one species and especially a keystone species will directly cause the extinction of other species

13. Extinctions Pictured: Extinct, Caspian Tiger Extinction is when the last individual of a species has died. Historical extinctions have occurred due to meteor impacts but current extinction rates are faster now than previously.

14. Extinctions • Problems for smaller populations or a decrease in population size • Loss of Genetic Diversity • Inbreeding depression • Genetic drift • Lack of gene flow, if isolated populations • Demographic Fluctuations • Environmental Fluctuations • Food Availability • These factors influence the Extinction Vortex

15. The Extinction Vortex

16. Human Impact causes deforestation and degradation to marine environments. This results in global warming, climate change, extinctions and a decline in biodiversity. How do we Conserve Biodiversity?