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Conservation and agricultural scenarios for western Zambia

Zambia has a large number of protected areas. Here we use WaterWorld 2.87 to compare scenarios of:

(a) intensive agricultural development outside these PAs at 10 trimes the current rate with the PA left intact to provide hydrological ES
(b) intensive agricultural development inside and outside of these PAs 
(c) eco-efficient agricultural development outside PAs including the use of buffer strips, low input techniques and terracing of steep slopes

Baseline hydrology

The baseline hydrology for western Zambia shows a strong north-south gradient in water balance reflecting the distribution of wind-driven rainfall and actual evapotranspiration coupled with inputs from fog.

Land use scenarios

In the intensive outside of PAs scenario (a) we apply the following rules:
Scenario namedef
Tree:10
Herb:80
Bare:15
continuing current rate of change for (years):100
multiply current rate by:10
fraction of forest degradation included:0.5
include planned roads (if available):no
include likely transport routes:yes
whereProtected areas (UNEP-WCMC WCPA) 2012
is=
this value:0
Land converted tocropland
Intensity of use1
...and see land use change throughout the unprotected areas of the region and this leads to increases in water balance for some regions and decreases for others according to the balance between change in actual evapotranspiration (decreases because of lower tree cover) and change in fog interception (also decreases in foggy areas because of lower tree cover), leading to decreases in runoff (though these are small in percentage terms) and an increase in the seasonality of the remaining runoff.  Significant increases in the human footprint on water quality also occur even in percentage terms at the sites of the new agricultural land and downstream.

In the intensive outside and inside of PAs scenario (b) we apply the following rules:

Scenario nameinpas
Tree:10
Herb:80
Bare:15
continuing current rate of change for (years):100
multiply current rate by:10
fraction of forest degradation included:0.5
include planned roads (if available):no
include likely transport routes:yes
whereBiodiversity hotspots (CI)
is>=
this value:0
Land converted tocropland
Intensity of use1
...and see land use change throughout the north of the country.   This leads to greater decreases in runoff though these are again small in percentage terms.  This leads to much greater human impact of water quality locally but the effect downstream does not change significantly.

The eco-efficient agricultural development outside PAs is a combined  scenario including land use change as per scenario (a) but also  the use of buffer strips, low input techniques and terracing of steep slopes.  The scenario is complex as:

Stack 0 | VariableValue
Formlanduse_change
Actionrunmodel_do
Scenario namecons
Tree:10
Herb:80
Bare:10
continuing current rate of change for (years):100
multiply current rate by:10
fraction of forest degradation included:0.5
include planned roads (if available):no
include likely transport routes:yes
whereProtected areas (UNEP-WCMC WCPA) 2012
is=
this value:0
Land converted tocropland
Intensity of use1


Stack 1 | VariableValue
Policy namecons
Tree:100
Herb:0
Bare:0
within distance (metres) of streams60
whereCover of tree-covered ground
is<
this value:20
Land converted toprotected
Intensity of use1


Stack 2 | VariableValue
Formland_management
Actionecoefficient_ag
Policy namecons
Develop eco-efficient agriculture on % of agricultural land100
whereCover of tree-covered ground
is<
this value:20
Intensity of use0.5


Stack 3 | VariableValue
Formland_management
Actionbench_terracing
Policy namecons
Create bench terrace on % land100
where slope gradient>25
and whereCover of tree-covered ground
is<
this value:20



...and the implications are a change in the distribution of croplands, forests, protected areas, cropland intensity and slope gradient.  These conservation focused changes lead to increases in water balance in some areas and decreases in others relative to the baseline, resulting in an overall increases in runoff in some areas and decreases in others.  Impacts on water quality are significant in the agricultural areas but, because of the low input regimes and the user of riparian buffer strips of these areas, do not propagate far downstream.  In some areas water quality improves compared to the baseline as existing agriculture comes under better management.