Numbers of Insects (Species and Individuals) It has long been recognized and documented that insects are the most diverse group of organisms, meaning that the numbers of species of insects are more than any other group. In the world, some 900 thousand different kinds of living insects are known. This representation approximates 80 percent of the world's species. The true figure of living species of insects can only be estimated from present and past studies.
Retaining Wall Cost. Poured retaining walls with elaborate curves require complex formwork and will drive up cost for a wall. The total cost to have a concrete retaining wall installed will be a combination of material and labor prices. For a basic wall you can expect to pay between $30 and $40 per square foot.If you add a decorative finish, curves, steps, lighting or other upgrades, the cost will rise.or Ralston, $39 per square foot is the average cost he charges for a wall under 4 feet tall. For walls below 4 feet, he says his prices are often competitive with finished block. A block wall has to be stuccoed or finished with veneer, while a concrete wall does not need an added finish.
Wood Retaining Wall Prices. Wooden retaining walls start at around $20 per square foot including materials and installation if using cost-effective pressure treated lumber. Hardwoods such as redwood, Cyprus or mahogany will raise the price over $30 per surface square foot but add an element of beauty to your wall.Railroad ties are the most commonly used wood for a retaining wall, and prices for this type of wall cost between $25 and $30 per square foot of wall.tone Retaining Wall Prices. Stone retaining wall costs typically start around $5 to $10 per surface square foot of wall. They can reach higher if a specific type of stone is used.