What claim can be made about the trends in net primary productivity shown in the diagram? Responses Productivity is greatest along the coasts due to ocean currents, which is why western South America has such a high rate. Productivity is greatest along the coasts due to ocean currents, which is why western South America has such a high rate. Photosynthesis takes place in areas where rainfall is heaviest, so northern areas are the most productive. Photosynthesis takes place in areas where rainfall is heaviest, so northern areas are the most productive. Polar regions lack the same rates of productivity as other places because these areas are far too cold for photosynthesis to take place. Polar regions lack the same rates of productivity as other places because these areas are far too cold for photosynthesis to take place. The southern hemisphere received more intense solar radiation than other areas, so productivity rates increased.