The Oil Drum

I wonder if the Big Island could technically be food self-sufficient?

Not with its current population.  

First lots of water - essentially irrigation to protect against drought, where the water is pumped from underground aquifers.

Secondly fertilizer - generally made from natural gas.  Essentially because monocultures tend to strip the nutrients from the soil (called by some mining the soil), so there is this constant need to replenish these nutrients.

Finally pesticides - generally also petrochemicals of one sort or another.

Of these, we have already talked a lot about limitations involving both oil and natural gas, so let me focus on water instead:

http://en.wikipedia.org/wiki/Ogallala_Aquifer

The Ogallala Aquifer, also known as the High Plains Aquifer, is a shallow water table aquifer located beneath the Great Plains in the United States. One of the world's largest aquifers, it lies under about 174,000 mi² (450,000 km²) in portions of the eight states of South Dakota, Nebraska, Wyoming, Colorado, Kansas, Oklahoma, New Mexico, and Texas. It was named in 1899 by N.H. Darton from its type locality near the town of Ogallala, Nebraska.

The regions overlying the Ogallala aquifer are some of the most productive regions for ranching livestock, and growing corn, wheat and soybeans in the United States (often called the "breadbasket of America"). The success of large-scale farming in areas which do not have adequate precipitation and do not always have perennial surface water for diversion, depends heavily on pumping groundwater for irrigation.

The aquifer was first tapped for irrigation in 1911. Large scale use for irrigation began in the 1930s and continued through the 1950s, due to the availability of electric power to rural farming communities and the development of cheap and efficient electric turbine pumps. Because the rate of extraction exceeds the rate of recharge, water level elevations are decreasing. At some places the water table was measured to drop more than five feet (1.5 m) per year at the time of maximum extraction. In extreme cases, the deepening of wells was required to reach the steadily falling water table; and it has even been drained (dewatered) in some places.

Water problems aren't just a problem for agriculture.  There was a comment here at TOD about a place in Oklahoma where oil drilling had been suspended - the local town no longer had sufficient quantities of water required to support the drilling.

http://www.theoildrum.com/story/2006/2/22/122330/042#2

You might see more electric vehicles getting used in agriculture, making a more direct use of that wind.. either that, or that farmers would commit a portion of their cropland for biofuel that would be grown to assist in their own energy needs.  If anybody can find a way to improve eroei, I'll bet a farmer can.. the original scientists.

"I assume total food production globally has peaked or will peak very soon."

This is the most perceptive, and most alarming, observation I have read in some time. It condenses and encapsulates most of the biodiesel discussion we've been having, as well as many other threads.

Think about this: roughly half of the nitrogen in human biomass comes directly from the natural gas based fertilizers. As we hit peak gas, we probably hit peak food.

In addition, half of cropland use prior to the invention of the internal combustion engine went to feeding horses and oxen for primary power and transportation. The conversion of this cropland to direct human consumption helped feed the green revolution.

Now it looks like we'll be drifting back to having half our cropland go for transportation; but via biofuels and ethanol.

Thus, we should expect the decline after "peak food" to be quite steep. Very sobering.

Another downside is that 19th century cities had large crews sweeping up horse manure, to be transferred to farmers in surrounding farms, which produced food for the cities. There don't appear to be such manure production possibilities from vehicular transportation.