Environmental Engineering Reference
In-Depth Information
Table 5.1
Degradation facts and figures (continued)
Water quality and river health
Agricultural activities affect water quality and the environment in the following ways:
•
extraction of water from rivers and groundwater for irrigated agriculture severely
affects ecosystems of rivers, wetlands and estuaries. The drainage water that returns
from irrigation could be heavily polluted by high loads of salt and agricultural
chemicals
•
irrigation uses rivers and wetlands as storages and conduits, thus distorting river and
wetland flow regimes
•
run-off from rural land carries sediment, nutrients, organic matter and agricultural
chemicals
•
land clearing and irrigation activities cause rising watertables and salinisation of
rivers and wetlands.
extensive loss of native vegetation is now resulting in massive changes to eco-
system processes and considerable loss of native species.
It is a worthwhile proposition that retaining and/or increasing the native
vegetation cover in a landscape will help to retain the native biota (flora, fauna
and micro-organisms) and control most land and water degradation. To
establish the basis for this concept, it is important to define ecosystem goods
and services and to understand how they are often lost as degradation occurs.
'Ecosystem goods' are the products we harvest from ecosystems. Pasto-
ralism and forestry depend heavily on ecosystem goods: pastoralism in the
rangelands is based on forage produced by native plants; forestry depends
exclusively on ecosystem goods such as soil, nutrients and water. Extensive
agriculture also depends heavily on them, but mainly on goods such as
cereal crops, domestic livestock and fruit that originated from outside Aus-
tralia. The array of goods is increasing as landowners begin to find value in
natural products in addition to the traditional livestock and agricultural
crop products.
'Ecosystem services' include activities such as removal of carbon dioxide,
production of oxygen, disposal of wastes, pollination, regulation of the
hydrological cycle and maintenance of nutrient cycling.
Most of the biodiversity in agricultural landscapes occurs in the soil.
Farmers know that maintaining soil fertility is the basis of all agriculture.
They also know it is expensive to keep applying fertiliser, and that acidifica-
tion, salinisation, compaction, loss of structure and erosion are serious
problems that greatly reduce profitability. A common reason for these forms
