Skip to main content

Table of Contents

  1. Introduction: AIACC: Climate Change and Conservation Planning
    1. Chapter1: Evidence for climate change
      1. Chapter 2: Global circulation models
        1. Chapter 4: Biodiversity responses to past changes in climate
          1. Chapter 5: Adaptation of biodiversity to climate change
            1. Chapter 6: Approaches to niche-based modelling
              1. Chapter 7: Ecosystem function modelling
                1. Slide 1: Ecosystem function modelling
                2. Slide 2: Aspects and levels of biodiversity
                3. Slide 3 : Dynamic Vegetation Models
                4. Slide 4: DGVMs continued...
                5. Slide 5: A 'reduced form' ecosystem model for savannas under climate change
                6. Slide 6: Basic savanna system model
                7. Slide 7: Water balance modelling
                8. Slide 8: Controls on grass growth at the annual timescale
                9. Slide 9: Linear relation between grass production and rainfall
                10. Slide 10: Slope: Rain Use Efficiency (g/m2/mm)
                11. Slide 11: Intercept: dependent on soil water holding capacity; co-varies with the rain use efficiency
                12. Slide 12: Effect of trees on grass
                13. Slide 13: Maximum tree basal area
                14. Slide 14: What controls the growth rate of trees?
                15. Slide 15: Effect of CO2 on NEP
                16. Slide 16: Effects of temperature on NEP
                17. Slide 17: What controls tree mortality?
                18. Slide 18: Mammal dynamics
                19. Slide 19: Keeping it together!
                20. Slide 20: Test 1: trees, grass and fire
                21. Slide 21: Test 2: + herbivores, carnivores
                22. Slide 22: Test 3: + elephants
                23. Slide 23: The experiment design
                24. Slide 24: Change in production drivers
                25. Slide 25: Change in vegetation structure
                26. Slide 26: Change in herbivores
                27. Slide 27: Preliminary conclusions
                28. Slide 28: Test yourself
                29. Slide 29: Links to other chapters
              2. Chapter 8: Climate change implications for conservation planning
                1. Chapter 9: The economic costs of conservation response options for climate change
                  1. Course Resources
                    1. Practical: Conservation for Climate Change
                      1. Tests to Assess your Understanding
                        1. How to run a GAM model in R

                          Slide 22: Test 3: + elephants

                          Duration: 00:01:27


                          Adding elephants into the system, however, throws things completely out of kilter. Since elephants are known to prefer browsing (although they can survive as grazers as well), their impact on the tree population is considerable. The proportion of grass grows very rapidly, and both tree basal area and tree height drop to a low stable (coppiced point), as the elephants push over the larger trees and coppice the smaller ones. This stable, highly productive coppiced tree population is optimal for supporting elephants, since the level of production is so much higher than fully-grown trees.

                          The elephant population climbs rapidly from an initially moderate level to a very high one (in excess of 4t/km2). Even more importantly, the browsing pressure from elephants would push the browser population into competitive collapse before 2040, and then a shift in diet to include more graze would cause the coarse grazer population to crash within the next 25 years. The main reason for this is that there are no real predators for elephants, and the question that follows is why has this effect not been observed in nature? It seems the most probable reason is that there is no such thing as an undisturbed wild population, as hypothesized. For tens of thousand of years, the top predator in the African savanna has been the human, and in fact the hunter of our ancestors is the only reason we are not knee-deep in elephants today.