Part III referred to these tiny single-cell plants

Global warming, climate change, fossil fuels, carbon emissions, rising CO2 levels - excuse the pun but these are hot topics.

BUT are we missing something in the bigger picture on planet Earth?

Destruction of the rainforests and planting of more trees world-wide are important topics in many ways. Their contribution to removing CO2 from the atmosphere via photosynthesis is well understood.

However, all the trees and plants on Earth account for only 28% of the oxygen we breathe.

In reality, we owe every breath we take to marine flora mostly invisible to the naked eye. 70% of the oxygen in the atmosphere is produced by marine plants and the majority comes from phytoplankton (with kelp and algal plankton etc as the other producers). All these marine plants are sensitive to chemical pollution. If we lose them then terrestrial production of oxygen is insufficient to maintain human life regardless of how many forests we save or trees we plant.

It is generally accepted there are natural cycles of cooling and warming of the oceans but it is increasingly difficult to ignore man’s input into increased carbon emissions as a causal effect.

Why are the oceans warming? Is it just because of our increased carbon emissions? Or is there more to it than that?

Here’s the scary part - some scientists believe that phytoplankton levels have declined by 40 % since 1950 with the most likely cause being global warming. That is not only a massive decrease in the conversion of CO2 into O2 but also a massive reduction in the food source for krill and on up through the food chain. Scientists believe krill have declined by 80 per cent since the 1970s, and the most likely cause is again global warming.

Oceans have absorbed up to 30 per cent of human-made carbon dioxide around the world, storing dissolved carbon for hundreds of years. As the uptake of carbon dioxide has increased in the last century, so has the acidity of oceans worldwide. Since pre-industrial times, the pH of the oceans has dropped from an average of 8.2 to 8.1 today. Projections of climate change estimate that by the year 2100, this number will drop further, to around 7.8 — significantly lower than any levels seen in open ocean marine communities today. This will have a dramatic effect

But is it just warming of the ocean? Without a doubt, increasing chemical pollution is adding to the problem. But are there other underlying reasons that initiated the problem prior to the 1970s?

Part V will look into this