Global Vegetation Production and Human Activity

1. Global Vegetation Production and Human Activity NRM 12-A: By: S.D. Prince and M.E. Geores Presented by Godfried Kwadjo Adjepong October 20, 2009

2. The study • Background: Data from orbiting satellite are used to measure global vegetation primary production. • Fixed carbon as source of food, fuel, and fiber • Primary production used to detect degradation • Goal: study the relationship between human dimensions of natural resource availability and primary production on a global scale.

3. Initial approach • Worked in conjunction with other models • To determine the difference between actual and potential primary production using a global 0.5 degrees * 0.5 grid. • Result: Suggested that part of the land surface are functioning at close to their climatically determined maximum, while others is of potential • Explanation requires combined human and biophysical approach

4. Methodology • Used Advanced Very High Resolution Radiometer (AVHRR) sensor • Permits temporal scales:10 days to 16 yrs, and spatial scale: 20 sqkm to covering entire globe • Observations: vegetation cycles – interannual variations in net primary production • Pattern are correlated with climatic variables • Combined 10 days or more of daily observations

5. Method- continue • Visible /near infrared spectral vegetation index (SVI) was employed • Normalized difference vegetation index (NDVI) was most commonly used with the AVHRR observation • Disruption of precise interpretation of spatiotemporal patterns in vegetation systems is possible • But analysis of AVHRR satellite data show strong correspondence to vegetation. • Particularly NDVI-time curve (∑NDVI.days)

6. What happened • Results: structured but poorly correlated distribution • Effect of temperature and precipitation

7. Limiting factors approach • To relate ZNDVI.days to temperature and precipitation -Bounding lines are defined joining max ZNDVI values of climate variable -Anticipated temperature- ∑ NDVI.days and precipitation- ∑ NDVI.days is known • Predicted ∑ NDVI days derived from climatological data --potential vegetation prod limited only by biophysical factors, while the observed ∑ NDVI.days –actual production.

8. Results A) Actual B) Potential C) Difference between the two in NDVI .days

9. Primary production and population of India A)Actual production B)Potential production C)Difference b/n actual production in NDVI.days D)Population density of India

10. Testing the hypothesis that human activity is the principal cause of deviations in production from potential values

11. Data from India • Proposition: Land cover is altered most in areas with the highest population density • Actual prod (item A) is far below its potential (B) • Areas with greater potential for production are more densely populated than others. • Relationship b/n primary production and population is not constant

12. Other factors • The global difference image confirms the need to consider additional descriptors of human activity • Population structure, level of economic development, and intensity of agricultural practice are related to actual production in regions having same potential for prod.

13. Conclusion • The observations suggest relationships b/n human activities and the difference b/n actual and potential vegetation prod on a global scale. • Notwithstanding the impossibilities in having controlled experiments • There is increasing concern for the world’s natural resources, thus the importance for global scale study.

14. Thank U Any questions