Soil salinization―the process by which soil acquires excess soluble salt, adversely affecting pasture or crop growth―is regarded as Australia’s most serious environmental problem. Cope, whose 1958 investigation is considered the earliest survey of salt-affected areas in Victoria, hypothesized that surplus rainwater mobilized soluble salt stored in the permeable layer of soil, causing it to accumulate above an impermeable layer and then discharge downslope or onto a valley floor. In the late 1970s, however, Jenkin identified saline water underground as the main and immediate (though not ultimate) source of the salt, and hypothesized that the spread of salinity resulted from a rise in that groundwater. He attributed the rise to a decrease in coverage by water-absorbing trees and other vegetation at some ill-defined point in Australia’s post-settlement history.

Soil salinization―the process by which soil acquires excess soluble salt, adversely affecting pasture or crop growth―is regarded as Australia’s most serious environmental problem. Cope, whose 1958 investigation is considered the earliest survey of salt-affected areas in Victoria, hypothesized that surplus rainwater mobilized soluble salt stored in the permeable layer of soil, causing it to accumulate above an impermeable layer and then discharge downslope or onto a valley floor. In the late 1970s, however, Jenkin identified saline water underground as the main and immediate (though not ultimate) source of the salt, and hypothesized that the spread of salinity resulted from a rise in that groundwater. He attributed the rise to a decrease in coverage by water-absorbing trees and other vegetation at some ill-defined point in Australia’s post-settlement history.

However, more-recent research suggests there was no rise in post-settlement groundwater levels. Furthermore, soil salinity probably antedated European settlement: early cartographic evidence indicates that some streams were saline when Europeans arrived. Dahlhaus suggests that salt accumulation resulted from marine incursions several million years ago, when parts of Victoria may have been submerged―as well as from transport of salt from the sea by wind and rain. Dahlhaus also notes that various minerals dissolved in groundwater by weathering may have produced salt.

The passage is primarily concerned with discussing
A . the chronology of various failed attempts to understand the dynamics of soil salinization in Victoria
B . the evidence concerning the approximate date at which soil salinity became a problem in Victoria
C . the degree to which the farming practices of European immigrants affected soil and water in Victoria
D . what research suggests concerning how tree coverage in Victoria has affected the absorption of saline water by soil
E . what best accounts for soil salinization in Victoria based on the results of research

View Answer

Answer: E