How is Lake Chad's current shrinking different than shrinking in the past?

Question

According to Wikipedia (http://en.wikipedia.org/wiki/Lake_Chad ):

"Lake Chad is believed to be a remnant of a former inland sea which has grown and shrunk with changes in climate over the past 13,000 years....Climate change, due in part to global warming, and increased demands on the lake's water have accelerated its shrinkage over the past 40 years....It seems likely that the lake will shrink further and perhaps even disappear altogether in the course of the 21st century....The lake nearly dried out in 1908 and again in 1984 and has an average depth of only 1.5 metres."

If Lake Chad has shrunk repeatedly in the past, then why is it now so worrisome? Is its current shrinking part of a normal cycle for the lake, or is global warming (or human usage or something else) making this worse than the past shrinkages? Is this shrinking permanent?

Lake Chad is often used as a prime example of global warming, but I don't understand how the current shrinkage is different than in the past.

Answer 1

You have a reasonable argument that current shrinkage may not be that different from the past:
This from USGS web site:
Fluctuations are not new to Lake Chad. About 10,000 years ago Lake Chad almost filled its present drainage basin, and spilled southwest out the Benue River to the Atlantic. In the last 1,000 years, according to fossil evidence, the lake probably dried out a half-dozen times. (Most of its fish are river-adapted species.) Geologic data, climate data, historical accounts and reconstructions all indicate a higher long-term variability than the relatively short period we have actually measured. The chart shown here shows levels since the 1870s, from actual measurements and from estimates based on Nile River discharge.6

Following highs in the 1870s and 1890s, the lake dropped enough by 1908 to separate into north and south pools, with the "Great Barrier" between. In the 1950s the lake rose enough to flood out irrigation systems, peaking this century in 1962. The lake then tapered off until the early 1970s, when it plummeted. The recent low levels are a concern, and have been monitored through satellite and other means by the Lake Chad Basin Commission and others.==url below

Whether or not it has dried out in the past, people have come to rely on it. Worrisome, I'm sure, to government agencies concerned with food supplies, irrigation, biodiversity, water availability etc. And I would suppose that any future increase in drought or temperature warming would guarantee a smaller lake, or its disappearance again.