Aquatic pollution is still a serious issue

Tiistai 28.3.2023 klo 15:53 - Mikko Nikinmaa

 In 1970’s and 80’s rivers were little more than sewage channels, and most waste water was pumped out to lakes and seas virtually uncleaned. If strands started to get littered, the solution was to make sewage pipes longer. A standing “joke” was that Americans built holiday resorts to Central America so that whenever the beach started to suffer from municipal pollution, that resort was left to locals and a new one built elsewhere. The polluted rivers could catch fires and fish deaths were common. In the Baltic Sea at least 70 % of the seals could not reproduce, almost causing extinction of Baltic seals.

One would have thought that humankind would have learnt from the problems of the past. But no. Profit is still the major goal; environmental actions are only done, when immediate financial gain would suffer from not doing them. Admittedly, water purification has been much improved in the industrialized countries in fifty years. In part, however, this has meant that the most polluting industry has been relocated to countries with lax environmental regulation. Some rivers in India have so high antibiotic levels that a patient could get a daily dose of medicine by drinking river water, others in Pakistan have so high effluent load from tanning industry that the water colour shows which dye is used most in the textiles. Even in our Western World, many improvements are not real. When it became clear that chlorinated compounds were highly toxic, they were banned. The chemical industry then started producing new fluorinated compounds. Anyone with reasonable knowledge of chemistry could have predicted that since fluorine and chlorine are sister elements, also fluorinated compounds are very toxic. This conclusion was finally reached, and several fluorinated compounds are banned. The insecticide use all over the world has increased, and one of the problems in their use is, if a sweeping generalization is made, that they are much more toxic to aquatic animals than to insects. Also, an occasional spill of toxic substances to rivers still occurs. Add climate change on top of all that, and the present-day situation emerges. The reason for including climate change is that first, the increase in temperature is a stress, and combined with contaminant-induced stresses can cause mortality, and second, climate change causes marked variations of river flow (because of alternations between heavy rains and dry periods) whereby the contaminant flow, e.g., from agriculture becomes highly pulsatile.

One sees the results in the news items. There have been massive fish mortalities in many shallow European lakes and in sea areas at Australian coast. Gold mining effluents have caused fish mortalities in Amazonas area and in Danube. The river Oder (in Poland) experienced major mass mortality of fish last summer and Murray and Darling rivers (in Australia) just recently. While the ultimate reason of neither is clear, agricultural toxicants together with climate change have likely contributed. About 30000 l of styrene leaked last Friday to a tributary of Delaware river, where Philadelphia obtains its drinking water, making it unsuitable for human use for a few days…These are just a couple of examples, it appears that there is an issue with aquatic pollution more or less every day somewhere in the world.

Kommentoi kirjoitusta. Avainsanat: fish mortality, climate change, multiple stresses, insecticides

Feeding people - Agricultural practises and land use

Lauantai 19.1.2019 klo 12:20 - Mikko Nikinmaa

Ohdake.jpgOut of the world's area, 71 % is sea and 29 % land (including inland water). Out of this 29 %, about 71 % is habitable. About 50 % of this habitable area is used for agriculture: the area is much larger than that occupied by real forests (36-37 %), scrubland (10 %, much of this is eroded farmland) or urban areas (2 %). Most of the agricultured land is pasture (77 %). Thus, all the crops for human food are cultivated in less than 25 % of the agricultural area.

The absolute amount of land that is used for agriculture is not increasing any more. New land is taken into use more or less in the same area as is lost as cultivated soil becomes infertile. The new cultivated land is mainly obtained through deforestration in the tropics. This means the loss of biodiversity and a decrease of the carbon dioxide sink of the forests. 

Although the human population has increased markedly in the past fifty years, the amount of feed per capita has also increased. This has happened via "green revolution", the increased yields per area partly as a result of the use of artificial fertilizers, irrigation, pesticides and high-yield strains of cultivated plants. There are, however, several downsides of the high-efficiency agriculture. First, it depletes the soils, which can become uncultivable. However, even if the fertility of the soil can be maintained with the use of artificial fertilizers, they leach in the inland waters, which are a limiting commodity anyway, and their eutrophication generates all sorts of problems for aquatic life. Irrigation improves the immediate water availability in cultivation, but it leads to overall decrease in ground- and lake water, as seen in Aral lake, Israel and California. Decreased groundwater levels can be one of the reasons for the Californian wildfires. Artificial fertilizers are, further, mined, and easily reached sites are more or less depleted. The use of pesticides is counterproductive, since non-target species are affected. Because of marked insecticide use it has already been suggested, and the results indicate clear correlation, that the decrease of beneficial pollinator populations is caused by the indiscriminate use of insecticides. The above examples indicate that the yield increases of "green revolution" may be temporary, and carry a heavy cost to the environment.

In view of this, it appears that there are three possibilities to decrease the need for inreased agricultural land use. All of these are also important ways to combat climate change. The first is to limit population growth. To do this, especially women's education should be improved. The second is to decrease the number of farm animals, especially ruminants whereby the proportion of agricultural land as pasture fields can be decreased and crop cultivation increased. This will decrease the amount of methane produced. Third, production ofedible plants close to their sites of consumption, e.g., aquaponics in cities, should be encouraged. This decreases transport distances for agricultural production.

Kommentoi kirjoitusta. Avainsanat: climate change, erosion, insecticides, biodiversity