Agriculture Reference
In-Depth Information
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
Table 33.1 A comparison of various methods for land degradation assessment
Factors
Scales
to which
Method
Advantages
Problems
applicable
applicable
Relative cost
Expert
opinion
Rapid, low
cost
Subjectivity,
reliability
Applied at
global, but
potential for
all scales
Soil,
vegetation,
water
Low
Remote
sensing
Fairly rapid,
objective,
Large area
coverage
Separating
change in
land use from
degradation
Global,
regional,
national,
local
Vegetation,
land cover
changes
Moderately
low
Field
mo
nitoring
Directly
indicates
change in
condition
of land,
quantitative
Slowness and
high cost
Local, plus
district to
national on
sampling
basis
Soil,
vegetation,
water,
biodiversity
Relatively
high
[425
Line
——
0.8
——
Shor
PgEn
Pr
oductivity
changes
Degradation
is defined in
these terms
Variations in
management
practices
National,
district, local
Crop
production,
animal
production
Low at
national, high
at local levels
Field criteria
and talking
wi
th farmers
Acquires
grass-roots
view, links
degradation
with cause,
impact,
response
Slowness,
subjectivity
Local; district
on sampling
basis
Soil (includ-
ing erosion),
vegetation,
water, bio-
diversity, so-
cioeconomic
indicators
Relatively
high,
practical only
on sampling
basis
[425
M
odeling
Rapid,
low cost,
potential for
extrapolation
Danger that
users confuse
modeling
with results
All scales
Soil, water
Relatively
very low
Source: FAO (2000).
Ea
rly Warning Systems
At international levels, there are groups that alert user communities to en-
vironmental changes. For example, the World Meteorological Organiza-
tion's (WMO) early-warning system (
www.wmo.org;
chapter 31) is com-
posed of weather satellites and thousands of surface monitors. This system
has helped predict long-term droughts and provided information for other
human-induced disasters.
Another example of early warning at the international scale is FAO's
Global Information and Early Warning System (GIEWS; chapter 32). The
GIEWS reports the production, stocks, and trade of cereals and other basic
Search WWH ::
Custom Search