Use of Systems Theory, Directed Graphs, and Pulse Process Models in an Adaptive Approach to Agroecosystem Health and Sustainability - Integrated Assessment of Health and Sustainability of Agroecosystems - page 117

3. Te a production Gikabu

23. Private vets

1. KTDA

2. Lack of market
for tea

10. Inadequate
extension

5. Vermin

6. Farm labor
shortage

24. Dairy production

4. Te a estates

12. Low food-crop
production

8. Casual labor

7. Farm productivity

13. Food shortage

25. Limuru Dairy
co-operative

11. Crop diseases

14. Malnutrition 9. Income

27. Improper use of
income

22. Nazareth Hospital

15. Poor health

26. Lack of school
fees

17. Health care expensive
and/or far away

31. Insecurity

28. Alcoholism and
drug abuse

18. Water shortage

32. Plan International

21. Health Foundation

20. Wells dry up
in dry season

33. Poor upbringing
& lack of discipline

30. Lack of formal
employment

16. Community's inability
to organize itself

19. Rivers are
far away

29. Ignorance and
laziness

fIGuRe 4.7 A cognitive map depicting perceptions of factors influencing health and sus-
tainability in Gikabu intensive survey site, Kiambu District, Kenya, 1997. (KTDA: Kenya Tea
Development Authority.) See CD for color image and key.

process, the impacts of all community goals except tea markets remain as shown in
Table 4.10. Tea market produces oscillating impacts at most vertices that are indeter-
minate through the geometric analysis except vertices 15 and 31, where it has posi-
tive impacts. The only impacts that are sensitive to changes in the weight of the arcs
are those of tea market on vertices 9, 13, 14, 15, 18, and 26 through 31.
The digraph consists of three main strong components. The first is pulse stable
and consists of 4 vertices (2, 3, 4, and 5) in two negative-feedback loops. The second,
consisting of 12 vertices (7, 9, 13, 14, 15, 18, 26, 27, 28, 29, 30, and 31) in 15 positive-
feedback loops, is unstable. The third component comprises vertices 23, 24, and 25
in two positive-feedback loops and is pulse stable. The first strong component can
be value stabilized by removing any one of its arcs except [4, 5]. Among the simple
ways of value stabilizing the second component is removal of arcs [9, 26] and [9, 18],
inversion of arc [9, 13], followed by inversion of any one of arcs [27, 28], [26, 29],
[28, 29], and [29, 28]. The third component can be value stabilized by inverting any
one of its arcs.

4.3.6 t h i r i r i k A
In the cognitive map depicting perceptions of the Thiririka community on factors
influencing health and sustainability (Figure 4.8), vertex 7 has cognitive centrality
with a total degree of 10. Other vertices with high total degrees are 26, 3, and 4, with