Biology Section 3.5 The Biodiversity Crisis
-One of the costs associated with human overpopulation and development is an accelerated extinction rate
-Current extinction rate is high enough to match the great mass extinctions of the past
MASS EXTINCTION – large scale dying out of a large percentage of all living organisms within an area over a short time
-Threat to species diversity is called the biodiversity crisis
BIODIVERSITY CRISIS – current decline in genetics, species, ecosystem diversity that may represent a mass extinction
The Threat of Climate Change to Biodiversity
-Threats: habitat destruction, competition from invasive species, illegal trade, pollution, climate change (changing patterns of precipitation and temperature)
-Examination of long term data (such as flowering times of plants or migrating times of birds)
-Exposure of organisms to changed climates in controlled settings to measure results
-Use predictions of climate scientists about future precipitation and then measure the result
-Make future predictions about impact on climate change
MODELLING – scientific method in which an idea about a mechanism is formulated and real life data are then used to see if the data fit in the model
Climate Change and Food Sources
-2009 study reported caribou and reindeer populations throughout world have decreased by almost 60% over the last three decades
-Warmer summers favour plant growth over lichen growth (lichens being the primary winter food source of caribou)
-Winters have more precipitation causing more snow or freezing rain thus reducing the ability for caribou to access lichen
-Earlier springs result in earlier plant growth in northern regions thus when migrating caribou arrive, plants have already reached their peak growth and have lost most of its nutritional value
-Birth rate is declining, mortality rate is increasing
Climate Change and Habitat
-As altitude increases, plant communities change similar to the way they change with increase in latitude from the equator to the North pole
-Temperatures decrease with increasing altitude, producing different vegetation zones
-Plant communities thrive in warmer temperatures found at low elevations, vice versa
-There is less land near the top of mountain (upper zones smaller than lower zones) thus when warming trends shift upwards, it makes the zone smaller
-Snow bed plant communities consist of high altitude flowering plants that live in areaswhere snow accumulates during the winter
-Communities are vulnerable to upward shift
-Warming results in habitat loss, reduces amount of suitable land where plants can grow
-Remaining areas become more fragmented, leading to isolate plant populations leading to reduced genetic diversity
Climate Change and Reproduction
-In many reptile species, sex of offspring determined by temperature in which eggs are incubated
-Most Ontario turtles lay eggs in sand, eggs of several species produce females when temps are warm, males when cool
-Increase in temperature could mean too many females and not enough males
TEMPERATURE SEX DETERMINATON – system in which the sex of offspring is determined by incubation temperature rather than genes
-Tuatara lizard, warmer temps produce males, population unlikely to survive if 75%+ males
Climate Change, Plants and Animal Pollinators
-Pollen necessary for sexual reproduction in plants
-Plant and pollinator (insect, bird, bat) dependent on each other, pollinator needs plant for food, plant needs pollinator to move pollen from plant to plant
-Usually only 1 pollinator species per flower species
-Success depends on timing, pollinator must be in right stage of life or migration cycle to be present when the plant flowers
-Warmer temperatures unlikely to upset pollination relationship if plant flowers earlier and pollinator becomes active equally earlier
-Mismatched timing can mean unpollinated plants
-Upon spring emergence, pollinator finds plant to consume nectar
-Under altered conditions, insect emerges but plant not ready for flowering, thus insect doesn’t have sufficient food resources, and when plant is ready, pollen cannot be spread as effectively thus reduction in number of fruits and seeds that plants produce
Climate Change and Aquatic Ecosystems
-Increasing temperatures associated with climate change affect freshwater organisms
-Experiment that artificially warmed Toronto stream by 2-3 degrees increased invertebrate growth rates but population densities decreased
-Adult insects emerged earlier, male to female sex ratio changed, these insects were food for other animals
- Another experiment changed the water temperature of Lake Ontario by 2 degrees
- Warmer summer decreased appetite of fish, decline in growth rate
-Warmer winter, increased appetite of fish, increase in growth rate however they consumed more of dissolved oxygen in water, over the year, growth of fish was reduced and consumption of oxygen increased