They can number up to a million per hectare (2.5 acres).
The population of the district is 104,800 equating to just over one person per hectare.
In the 1930s land with vacant possession cost an average of £60 per hectare.
The cost of herbicides is high, from $198 to $297 per hectare.
Population densities range from 2 to 22 individuals per hectare.
The growing stock volume per hectare then was merely 6m3, 6% of the current figure.
The density of population was 115 persons per hectare in 2001.
Tobacco production involves up to 2 200 hours of work per hectare.
The fact that the report calls for aid per hectare is a positive thing.
This estimated figure shows much higher than the past year 1995 with only 11.54 persons per hectare.