Rivers and oceans are easily neglected when it comes to pollution. Out of sight, out of mind and all that. Except that the oceans do not forget. Of all the water pollution problems, oxygen loss is probably one of the more abstract ones. Even the words used to describe it, hypoxia and anoxia, will be meaningless to those without a background in biology. In Dead Zones, marine scientist and microbiologist David L. Kirchman provides a general introduction to the problem of oxygen loss and why it matters.

Dead Zones: The Loss of Oxygen from Rivers, Lakes, Seas, and the Ocean, written by David L. Kirchman, published by Oxford University Press in April 2021 (hardback, 224 pages)

I thought you could not tell me anything new on this topic. After all, for my PhD, I spent five years in Finland studying how fish behaviour in the Baltic Sea is affected by eutrophication, the pollution caused by excess nutrients. The Baltic is one of several badly affected water bodies in the world due to the large land area that drains into it and the narrow connection with the North Sea. However, my studies focused on decreased underwater visibility due to algal blooms rather than oxygen loss. Dead Zones was thus a welcome surprise and refresher, showing that even I had only an incomplete picture of the problem.

So what are dead zones? They are areas of fresh or marine water that have low (hypoxia) or virtually no (anoxia) dissolved oxygen. As Kirchman clarifies in his prologue, the term is a bit dramatic. It does not mean that the whole water column is affected, often it is limited to the bottom layer. And they are not always completely dead, some organisms actually thrive here. But many creatures are sensitive to oxygen loss, leading to slower growth, fewer offspring, and poorer health. In extreme cases, it leads to the death of fish and bottom-dwelling invertebrates, reduced biodiversity, and reshuffled food webs.

Dead zones vary in size through time, influenced by weather and currents. But since about the 1950s, they have been steadily growing both in size and number, and we know the cause. Fed by excess nutrients, algae bloom. When they die, the bacteria decomposing them use up oxygen quicker than it can be refreshed. But before we get to this point in our understanding, the first half of the book takes the circuitous route through the history of their discovery.

“[Dead zones] were a natural occurrence in the past, but the frequency and severity have increased, and it all centres on roughly 1950.”

Some of the first dead zones that were widely noticed were the Great Stinks. Not that long ago, many rivers running through bustling cities in Europe and the US received large loads of untreated sewage. The resulting bacterial feast would rapidly consume all the oxygen and then switch to sulfate metabolism, releasing hydrogen sulfide with its characteristic smell of rotten eggs. Wastewater treatment facilities brought this problem under control, with rivers recovering and fish returning.

Much harder to notice were the dead zones developing in coastal areas, such as the Gulf of Mexico or Chesapeake Bay, or inland seas, such as the Black Sea or the Baltic Sea. Kirchman takes you through their discovery in the 1980s and the research by Nancy Rabalais and others to address the question whether they have always been there? The answer required the meticulous collection of long time series of oxygen measurements and the study of sediment cores that record past oxygen levels. The conclusion is that, yes, they were a natural occurrence in the past, but the frequency and severity have increased, and it all centres on roughly 1950. How so? More nutrients, specifically nitrogen and phosphorus. Where did they come from? Artificial fertiliser used in agriculture. As discussed here, there have been naysayers, both in scientific circles and amongst farmers and industry, but the evidence is pretty convincing by now.

Although Kirchman does not explicitly mention it, the 1950s marks a transition period dubbed the Great Acceleration during which our impact on the environment boomed. And the increase in nitrogen and phosphorus release is one of many indicators used by scientists to define the start of the Anthropocene. Two key figures Kirchman introduces here are Fritz Haber and Karl Bosch. The former developed a process to cheaply and efficiently fixate nitrogen, the latter scaled it up for the industrial production of explosives and artificial fertiliser. The Haber–Bosch process was one factor facilitating the human population explosion driving the Great Acceleration. As Kirchman mentions, “Depending on your diet, about half of the nitrogen in your body came from a factory using the Haber–Bosch process” (p. 96), and Vaclav Smil is quoted as writing that, without it, Earth would probably have only half the human population it has now.

“[…] these problems have been […] difficult to tackle. One factor is the inherent complexity of the system. […] There is no one-size-fits-all solution.”

Having arrived at the status quo, the second half of Dead Zones explains why these problems have been so difficult to tackle. One factor is the inherent complexity of the system. Which nutrient is the limiting one runs the full gamut from nitrogen in marine waters (mostly) to phosphorus in lakes, and sometimes neither. There is no one-size-fits-all solution. Similarly, as Kirchman explains, fish kills are not a problem suitable for a bumper sticker slogan to rally behind: “Dead Zones Kill Fish and Fishery Jobs” (p. 128). The reality is more nuanced. Oxygen depletion can, for example, boost fish landings when fish flee hypoxic zones and become easier to catch. And this leads to the second factor: all these complexities make it very easy for those who stand to lose from tougher environmental regulations to call for more research, and for legislators to hesitate to implement anything. However, as Kirchman points out: “[…] we cannot ignore dead zones just because the effect of hypoxia is complex” (p. 133). To that end, he offers a range of solutions, including things that you, the reader, can do.

Dissolved oxygen levels in water was never going to win the prize for the sexiest topic. Given this inherent handicap, Kirchman’s conversational tone makes Dead Zones nicely accessible. However, I do feel that the overall structure and clarity suffer somewhat, although I cannot quite put my finger on the why. The narrative ricochets between different topics and some things are only touched upon (e.g. the rise of jellyfish, or the release of neurotoxins during certain algal blooms). I did enjoy the historical sketches, they are Kirchman’s forte. At only 172 pages, this book is not a thorough overview but more a general introduction. Since these topics are normally discussed in scientific journals, reports, academic monographs, and edited collections, it is an introduction that is long overdue.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

Dead Zones

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The 19th century was, for Europe and the United States in particular, a time of exploration and scientific study. Large parts of the world were still little explored and poorly mapped. Concurrent with the production of improved maps and atlases, there was a craze for a unique kind of infographic that has long since fallen by the wayside: the comparative tableau, showing the world’s highest mountains and longest rivers. This lush coffee table book sifts through the David Rumsey Historical Map Collection, one of the most renowned collections of its kind, to give readers a glimpse into the development and history of these unique images.

An Atlas of Geographical Wonders: From Mountaintops to Riverbeds, written by Gilles Palsky, Jean-Marc Besse, Philippe Grand, and Jean-Christophe Bailly, published by Princeton Architectural Press in September 2019 (hardback, 208 pages)

The first thing that will strike you is the size of the book, a landscape-format book measuring some 31 by 28 cm with a tactile, ribbed cover. Flipping through it quickly convinces you that this format is needed to do justice to the images.

The second thing to note is that this is a book with a bit of a backstory. It was originally published in French in 2014 by Fage Éditions as Le Monde sur une Feuille and for this Princeton Architectural Press edition has been translated into English. Philippe Grand is the publisher at Fage Éditions and is the editor of the book, while Jean-Christophe Bailly and the duo of geography and cartography historians Jean-Marc Besse and Gilles Palsky each provide a short introductory chapter.

Those are followed by a short chapter on what might very well be the progenitor of the comparative tableau, an 1805 image from the hand of Prussian geographer, naturalist, and explorer Alexander von Humboldt. He was a prolific polymath who achieved many things in his life. One of his achievements was the climbing of Chimborazo, a mountain peak in Ecuador that at the time was believed to be the highest in the world. It inspired him to draw a tableau that was published in his Essay on the Geography of Plants, showing plant distribution along the mountain slope and mentioning the height of other mountain peaks.

With these introductions out of the way, the bulk of the book consists of several themed galleries. Initially, cartographers designed and drew mountain tableaux. But rather than aiming for geographic realism, they bundled the world’s highest mountain peaks together into imaginary collages, allowing easy comparison. These could vary from the schematic (such as the 1820 image by Carl Ferdinand Weiland below) to the pastoral (see the next 1814 image by J.-S. Devèze de Chabriol).

Two things stand out in particular. One is the sheer diversity with which this task of making a comparative tableau can be achieved. Take for example below detail from an 1827 tableau by Philippe Vandermaelen where the mountains on different continents are shown in segments bounded by a box. A personal favourite is the second 1851 tableau below from James Reynolds, which shows mountains as exaggerated narrow spires.

The second notable thing is that each approach spawned many imitators. Maybe it was the image reproduction techniques of the time, but many tableaux were redrawn by several artists with so little variation that they looked like carbon copies of each other. Looking at them through today’s eyes it is hard not to think of the word “plagiarism”.

Together with an interest in mountain peaks, geographers and explorers were mapping river systems and trying to find their headwaters, naturally leading to comparisons of river lengths. The book includes a number of tableaux where rivers were rendered straightened out to allow comparison (although a striking exception was the 1834 image below produced by the Society for the Diffusion of Useful Knowledge in London).

I guess it was only a matter of time before certain clever clogs figured out that drawing the mountains ascending from left to right created an empty triangular space that could be filled with rivers of decreasing length from left to right. And thus was born the combined comparative tableaux showing both river lengths and mountain peaks (see below 1826 example by Bulla and Fontana). Here too, variations on the theme existed, as shown in the second 1885 image by William Hughes.

The comparative craze in the end even extended to waterfalls, and sizes of lakes and islands, leading to some very busy infographics, such as below 1851 image by John Tallis and R. Montgomery Martin. And not infrequently these images were combined with increasingly accurate world maps, such as the second 1854 image by Traugott Bromme. Ultimately though, by the turn of the 19th century, this type of image declined. As mentioned in my review of Why North is Up, warfare and military interests drove the development of technology, requiring both more accurate maps, but also providing new kinds of information to show on maps. It was the refinement of layer colours, or hypsometric tints, by John Bartholomew that was an important contributor to the decline of these tableaux. As noted in Palsky & Besse’s introductory essay, though, there has been a renaissance of these kinds of images, for example when comparing heights of modern skyscrapers. And the original images have lost none of their staying power (see for example the book cover of Darwin’s Evolving Identity, published in 2018).

An Atlas of Geographical Wonders is a feast for the eyes, using its layout to good effect to show off the wonderfully reproduced images. Where images are so large and detailed that they could not be reproduced in any legible form, they are often reduced, though for some notable examples double-page spreads show close-up details. Other, smaller images are shown at full size or shown only slightly reduced, allowing you to read labels. All of them come with captions with basic information on artists, year, source, size, and (often) details on the type of image. For many, one or two paragraphs add more information, highlighting notable developments as explorers refined their knowledge of our world, or adding other interesting tidbits of information.

Cartophiles can rejoice, as this book is a visual delight that will make a wonderful addition to their collections. But the phenomenal production values make this a very enticing book for anyone with an interest in historical maps and images.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

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An Atlas of Geographical Wonders hardback

Other recommended books mentioned in this review:

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