Broomgrass model, Zimbabwe

Tue, 13/03/2012 - 13:48 — administrator

ModelId:

broomgrass1

SimileVersion:

5.x

Co-View is a tool developed by CIFOR (the Centre for International Forestry Research) to help facilitators of natural resource management and stakeholders to articulate and explore a shared vision of the future and to develop strategies to achieve it. The following explanation of the background to the broom grass model is adapted from the CoView (Collaborative Vision Exploration Workbench) User Manual (see Web Links below).

The broom grass model was developed in a participatory modelling workshop in Zimbabwe. The focus of the workshop was on the question: “How can broom grass be harvested sustainably?”, and in particular on “Should broom grass be harvested by digging or by cutting?”. The modelling work also souht to explore the impacts of the differing harvesting methods on the broom grass resource, as well as the income that could be obtained from harvesting broom grass.

Equations:

Compartments

compartment: broomgrass = 75000

Flows
destroyed = (if burning_internsity==2 then Broom_Grass__in_Machije_Vlei else agriculture+decomposition+element([proportion_of_grass_by__digging_uprooting__or_cutting],1)*total_harvesting/300)
growth = (if frequency_of_burning*burning_internsity>0 and element([proportion_of_grass_by__digging_uprooting__or_cutting],3)>0 then grass_growth*Broom_Grass__in_Machije_Vlei+germination else 0)
total harvesting = (if Broom_Grass__in_Machije_Vlei==0 then 0 elseif harvest then(element([proportion_of_grass_by__digging_uprooting__or_cutting],1)+element([proportion_of_grass_by__digging_uprooting__or_cutting],2))*0.008*number_of_harvesters*quantity_harvested_per_person+element([proportion_of_grass_by__digging_uprooting__or_cutting],3)*0.012*number_of_harvesters*quantity_harvested_per_person else 0)

Variables
agriculture = 2
Percent of Machije converted to agriculture
alternative income sources = (1==0)
availability of transport = (if transport_cost<=10 then 1 else 0)
beauty = processing+bundling_with_tube_or_fibre
bundling with tube or fibre = 1
1 for tube
0 for fibre
burning events = 1
burning internsity = (if season>=6 and season<=10 and frequency_of_burning>0 then 2 else 1)
1 = low internsity burning
2 = high internsity burning
comfort = length
decomposition = 5
expected income after harvesting = number_of_brooms_made*market_price_per_broom-permit_price-transport_cost
expected income before harvesting = market_price_per_broom*2000-permit_price-availability_of_transport
frequency of burning = (if rules_enforcement>0.5 then 0 elseif season>=6 and season<10 then burning_events else 0)
germination = (if soil_moisture==1 then seeds else 0)
grass growth = 1-growth_rate*soil_moisture/K
growth rate = 5
harvest = any([time_of_harvesting]==season)
income = number_of_brooms_sold*market_price_per_broom-permit_price
K = 1000000
length = 1
life of broom = bundling_with_tube_or_fibre*ripe_or_unripe*length*whether_cut__or_dug_or_uprooted
maximum number of broom harvest per day = 100
no_of_permits = 150
number of brooms made = 0.99*total_harvesting
Number of brooms sold = availability_of_transport*number_of_brooms_made
transport]
market price per broom = 3+last(quality_of_broom)*season/(supply_from_other_sources+1)
number of harvesters = (if alternative_income_sources then 0 elseif permit_price0.5 then[5,10,85]else[80,10,10]) quality of broom = beauty*life_of_broom*comfort quantity harvested per person = maximum_number_of_broom__harvest_per_day rainfall = element([rainfall_this_month],season) rainfall this month = [193,185,70,32,7,2,0,0,4,28,91,128] Months of the year when harvesting is permitted ripe or unripe = (if element([time_of_harvesting],1)==6 then 1 else 0) 1 = ripe 0 = unripe season = fmod(time(1),12)+1 seeds = (if element([time_of_harvesting],1)==6 and burning_internsity==1 and season==6 then produce else 0) set harvesting season = [6,7,8,9,10] soil moisture = (if rainfall>100 then 1 else 0) supply from other sources = 1 1 = yes there is supply from elsewhere 0 = there is no availabiility time of harvesting = (if rules_enforcement>0.5 then [set_harvesting_season] elseif number_of_people_not_farming<0 then[set_harvesting_season]-3 else[set_harvesting_season]) time of sale = market_price_per_broom transport_cost = 2 Price in dollars to transport a bundle of brooms