Population Changes and Environmental Damage

1. Population Changes and Environmental Damage Due to natural causes, changes in climate, human activity, and the introduction of invasive, and non-native species

2. Natural Causes

3. Natural Causes • Population Densities change relatively little through time, although annual fluctuations in density occur in response to various factors. • Factors regulating population size are responsible for temporal fluctuations. These include the following density-dependent factors and density-independent factors.

4. Density-Independent Factors

5. Density-Independent Factors 1) Weather - unfavorable weather can limit breeding success or cause deaths in the population 2) Food Supply - abundance of food is often dependent on climate, and in poor years food supply may limit population size. 3) Habitat Limitation – seasonal or annual changes can affect resource levels such as nesting sites or availability of nesting materials. (2) and (3) help set a limit for Carrying Capacity of the habitat. Because they are more important at high densities, they can be considered density-independent or density-dependent factors.

6. Density-Dependent Factors

7. Density-Dependent Factors 1) Predation = focuses most intensely on eggs and young. • Acts more strongly at high densities. Keeps populations below the theoretical carrying capacity in some cases. 2) Competition = if resources are limiting, only a given number of individuals may persist in a given habitat (the number that can persist is the carrying capacity). • At at high densities (near the carrying capacity) it becomes very important. 3) Parasites and Disease = have the greatest effect at high population densities. Can be important factors regulating population sizes in some cases.

8. Climate Changes

9. Changes in Climate • Climate has been changing over hundreds and thousands of year • In response temperate zones shift from coniferous to deciduous with changes in the dominant species of trees. • Quick changes, can species keep up? • Increased burning of fossil fuels increases CO2 level

10. Impact of Changing Climate • Current difference between temp. at poles and equator is a major driving force for atmospheric circulation. • Warming happening more quickly at the poles • Will change atmospheric circulation patterns and rainfall distribution patterns • Higher temp = more evaporation and great ability of the atmosphere to hold moisture. • Some regions drier and some wetter • Increased droughts and increased rainstorms • Widespread water concerns – droughts, floods, water quality • Rising sea level

11. Effect on Populations • Rate of climatic warming could outpace the ability of species to migrate northwards. • Plant species that can’t migrate trap both themselves and other dependent organisms in inhospitable climates. • Remember, not all organisms can adapt to the environmental changes and evolution takes years!

12. Human Activity

13. Human Activity • Physical Alteration of Habitats • Responsible for 36% of known extinctions • Conversion • From natural habitat to human use • Fragmentation • Reduced habitat can not support the critical number during adverse years • Simplification • Removal natural debris such as of fallen logs and dead trees diminishes microhabitats.

14. Human Activity • Pollution • Oil spills • Chemical spills • Destroy or alter habitats • Urban sprawl

15. Introduction of Invasive, Non-native Species

16. Introduced Species • Displace native species • Reduce biodiversity • Reduce farm and forest productivity • Affect human and animal health • Contribute significantly to land degradation • Many introduced plant species have become invasive weeds, noxious weeds or both and are among the most serious threats to the natural environment.