Interactive Dynamics of Wildlife Populations, Human Health and Household Wealth. Matthew D. Potts

Transcription

1 Interactive Dynamics of Wildlife Populations, Human Health and Household Wealth Matthew D. Potts 1

2 Acknowledgments Collaborators: Ryan Marsh, Elaina Marshalek, Samuel Evans, Lauren Whithey Biodiversity, Health and Livelhoods Team: Justin Brashares, Lia Fernald, Louise Fortmann, Claire Kremen, Katie Fiorella, Chris Golden NSF Funding: GEO , CNH: Interactive Dynamics of Wildlife Populations, Human Health and Household Wealth in Rural Africa. 2

3 Biodiversity, Health & Livelihoods Overview Global concern about biodiversity loss. Wildlife is the primary source of animal protein and income for more than 1 billion people (Milner-Guilland et. al. 2003). Open question: How do we identify feasible strategies to improve peoples livelihoods and conserve biodiversity? Research to date has focused on linkages between wealth, income and wildlife consumption. - Today, focus on the missing link of health and explore how its inclusion impacts wildlife population dynamics and overall household wellbeing. 3

4 Bushmeat & Development Hunting in Madagascar 4 C. Golden - Madagascar

5 Bushmeat & Development Economics J. Brashares J. Brashares The bushmeat trade is a local to global market that is valued at billions of dollars per year 5

6 Bushmeat & Development Economics Wildlife Consumption & Wealth Distance to Wildlife Effects 6

7 Bushmeat & Development Health Global Anemia Prevalence 7

8 Bushmeat & Development Impact of Bushmeat on Hemoglobin Bushmeat could contribute app % of what iron supplements accomplish 8 If access to bushmeat is lost, there will be a 30% increase in the incidence of anemia C. Golden - Madagascar

9 Biodiversity, Health & Livelihoods Guiding Question How does the inclusion of health in household economic models impact wildlife population dynamics and overall household well-being? - focus on time to collapse of wildlife population under different assumptions of how health status impacts labor availability: reduces total labor reduces total labor & agriculture activity - track household labor allocation, utility, health as well as wildlife populations 9

10 Model Big Picture Track utility and nutritional status of a representative subsistence household in a developing country. In each time period, households allocates labor to hunting and agriculture so as to maximize utility in that period (not forward looking). Nutritional status determines total amount of labor available and is updated period to period. Wildlife population follows logistic growth with off take determined by hunting activity. Human population growing through time. Wildlife population goes extinct when population falls below 20% of carrying capacity. 10

11 Model Key Variables U t G t N t P t Utility of representative household at time t Wild game population at time t Nutritional status of household at time t Total population at time t 11

12 Model Utility Function Household consume three goods: agriculture products (a), wild meat (w), and market meat (m) s i B i where - elasticity of substitution - budget share U t =(B 1 a s 1 1 s 1 t M t =(B 3 w + B 2 M s 2 s 2 1 s 2 t s 1 B 2 M t s 1 1 s 1 s 1 1 t ) s 1 + B 4 m U t s 2 1 s 2 s 2 1 t ) s 2 a t B 1 w t m t B 3 B 4 12

13 Model Utility Function Household consume three goods: agriculture products (a), wild meat (w), and market meat (m) s i B i where - elasticity of substitution - budget share B 1 =0.8 B 2 =0.2 B 4 =0.5 B 3 =0.5 s 1 =1.1 s 2 =1.1 U t =(B 1 a s 1 1 s 1 t M t =(B 3 w 13 + B 2 M s 2 s 2 1 s 2 t w t s 1 B 2 M t s 1 1 s 1 s 1 1 t ) s 1 + B 4 m m t B 3 B 4 U t s 2 1 s 2 s 2 1 t ) s 2 a t B 1

14 Model Constraints Crop production: A = Yl f Hunting: Budget: R C 0 Labor: Discuss Later H = QG t l g where R = p aa + p w H C = p a a + p w w + p m m Q - catch per unit effort Y =1 Q = =0.5 p a =1 p w =5 p m =5 14

15 Model State Equations I Utility - no updating since it maximized in each period. Population: P t+1 = r p P t Game: G t+1 = rg t (1 + G t /K G ) growth rate carrying capacity QG t l g P + G t Note: Game extinct when it reaches 20% of carrying capacity r p =1.03 r =0.5 K G =

16 Model State Equations II Energy status (ES) in a time period t ES t = e m(w + m)+e f a E f l f + E g l g Nutrition: If ESt 1: If ESt 1: N t+1 = N t +(1 N t+1 = N t N t /dn N t )/dn If ESt ESmin: N t+1 = N min Labor dependence on nutritional status I. No impact: l f + l g = l total II. Impacts total labor: l f + l g = N t l total III. Impacts total labor & farm labor: l f + l g = N t l total 16 If N t <N c l f =0

17 Labor dependence on nutritional status I. No impact: Model State Equations II Energy status (ES) in a time period t ES t = e m(w + m)+e f a E f l f + E g l g Nutrition: If ESt 1: If ESt 1: If ESt ESmin: N t+1 = N t +(1 N t+1 = N t l f + l g = l total N t+1 = N min N t /dn N t )/dn e m =1.65 e f =1.00 E f =1.20 E g =1.00 dn = 10 N min =0.1 l total =1 N c =0.3 II. Impacts total labor: l f + l g = N t l total III. Impacts total labor & farm labor: l f + l g = N t l total 17 If N t <N c l f =0

18 Results to Date 18

19 Base Case (No Nutritional Impact on Labor) Population Labor 0.0e e e Time 1:tmax farm hunt Nutrition Game Time Game population crashes in ~ 300 time steps. Labor allocation shifts to farming due to higher utility gained from farming and lack of game Time Time Solved used GAMS

20 Nutrition Impacts Total Labor Population P 0.0e e e Time 1:tmax Game Time Game population crashes in ~ 350 time steps. Linking nutritional status to labor allocation increase time to extinction. Labor farm hunt Nutrition No qualitative change in labor allocation between hunting and farmer Time Time Solved used GAMS

21 Nutrition impacts total labor & critical threshold for farming Population P 0.0e e e Time 1:tmax Game Time Game population crashes in ~ 150 time steps. Labor farm hunt Nutrition Loss of ability to farm leads to rapid game extinction Time 21 Time Solved used GAMS

22 Preliminary Conclusions Incorporation of nutritional status and linking it to labor availability and allocation can dramatically change the time to extinction of wild game species. Results highly depending on assumption concerning functional relationships and parameter values. 22

23 Next Steps (Lots more work) Get good parameter values Track multiple households Add weather shocks Incorporate household savings Incorporate different preferences for wild versus market meat Make it forward looking (stochastic dynamic programming) 23

24 Thank You! Questions? 24