Like in most cities in the region, you will find busy suburb markets such as in Kicukiro or Kimironko in Kigali where one can buy fresh fish. But until you see a white box or two – like I did not too long ago – strewn about with clear markings that at least some of the fish was packed in China, one begins to appreciate the circumstances that have made this possible. Yet it will not be news to say that fishery productivity in the regional lakes has been foundering amid a confluence of factors, and not least climate change. I bring this up in reply to a respondent to this column last week who thought US politics “too complex for us to comprehend” when I brought up Donald Trump’s demagogic presence in the ongoing US presidential elections and his threat, should he become president, to scrap US’s recent ratification of the Paris Agreement on Climate Change. (See “Trump’s disdain for facts”, The New Times, October 1, 2016) Trump thinks global warming is a hoax “created by and for the Chinese in order to make U.S. manufacturing non-competitive.” But, The Donald aside, and to bring the reality closer home, I want to draw my respondent’s attention to Lake Tanganyika – surrounded by Tanzania to the east, Burundi to the north, the Democratic Republic of Congo to the west, and Zambia to the south – and its declining yield of fish attributed to climate change and the threat it poses to millions of livelihoods in these countries. Ongoing research on the lake indicates that intervals of prolonged warming and cooling in the last 1,500 years are linked with low and high algae productivity, respectively, showing a clear link between past temperature changes and biological productivity in the lake. This is characterised by the geology of the lake, the second deepest in the world at a maximum of 1,470 metres (compare with Lake Victoria which is only 80 metres at its deepest and, despite having more than double the surface area, holds only 15 per cent of the volume of Lake Tanganyika). Findings in a recent paper, “Climate warming reduces fish production and benthic habitat in Lake Tanganyika, one of the most biodiverse freshwater ecosystems,” suggest that global warming could be having a major role to play in fish depletion following the low algae productivity. Most of the animal species on Lake Tanganyika live in the upper 100 meters, including the valuable sardines (Dagaa in Tanzania, or Omena in Kenya). Below that, the paper explains, the lake holds less and less oxygen, and at certain depths, it is anoxic, meaning it has no oxygen at all. This means the lake depends on wind to churn the waters and send nutrients from the depths toward the surface as food for algae, which supports the entire food web of the lake. But as Lake Tanganyika warms, the mixing of waters is reduced, leading to less nutrients being funnelled from the depths toward the surface. Worse, more warming at the surface magnifies the difference in density between the two levels; even more wind is needed to churn the waters enough to ferry the nutrients toward the fish-dwelling upper layer, thus affecting the yields. That is the science of it, but there’s one thing to note: the warming and cooling of the lake in the last 1,500 years has been natural, but the current warming can directly be attributed to emission of carbon dioxide due to human activities. And thus the irony that the least to blame pay the heftiest price with the livelihood at stake by the lake. As I observed last week, the least developed countries, most of them in Africa, constitute 11 percent of the global population but the average carbon dioxide output across the continent is only 0.9 tonnes. An average citizen in the US, with just 5 percent of the world’s population, pollutes 17.3 tonnes of carbon dioxide. For this reason US politics have everything to do with us in the region, as elsewhere, and why it matters the world power ratified the climate change pact. Trump has his constituency, and it is true it is not for us to decide, but to safeguard our particular interests it is best if the demagogue doesn’t get elected. Twitter: @gituram
