Thirsty: Banana

On the coastal plain of Ecuador, between the Andes and the Pacific, the road from Guayaquil runs for an hour through nothing but bananas. The plants stand in rows three metres high, their leaves tattered by the wind, each one carrying a single bunch wrapped in a blue plastic bag, and every few hundred metres a cable runs across the road on which the bunches travel, hooked and swinging, to a shed where they are cut, washed and boxed. The boxes go to the port at Guayaquil, onto a refrigerated ship, and three weeks later they are a bunch on a shelf in Hamburg or Rotterdam or Los Angeles. Ecuador ships about a third of the bananas the world trades, and this plain is where most of them grow.

A banana carries about a hundred litres of water, and this article is about where it went: into the plant, which is one of the thirstiest in the field, through the wash tanks of the packing shed, and onto the leaves from the fungicide planes that fly over the plantations of the wet countries forty times a year.

A giant herb

The banana plant is a herb, the largest there is, and it has no wood; the thing that looks like a trunk is a tight roll of leaf stalks, soft enough to cut with a machete, and the plant grows from an underground stem that sends up a new shoot as each one fruits and is cut down. A shoot takes nine months to a year to flower and fruit, and in that year it puts out a dozen leaves of a square metre or two each, and through those leaves it moves water from the soil to the air at a rate that few crops match. A banana plantation in full leaf uses on the order of five or six millimetres of water a day in the dry season, which is 1,500 to 2,500 millimetres a year, and it will not tolerate a dry month: the fruit stops filling, the bunch shrinks, and the plant waits for rain.

That water is almost all green water in the method this site uses: rain that fell on the field and went back into the air through the leaves. The countries that grow bananas for export are the wet tropics, and on the Caribbean side of Costa Rica or in Mindanao in the Philippines the rain is two, three or four metres a year, more than the plant can use. There the blue water, from irrigation, is close to zero and the plant drinks the sky.

The number is small for a reason that has nothing to do with thrift. A plant that grows a bunch of twenty or thirty kilograms in a year on a few square metres, in a place where the water arrives free, has a low water cost per kilogram however much it drinks. A mango, on a tree that takes years to bear and grows in drier places, carries about 1,800 litres a kilogram; rice, on a flooded field, about 2,500. The banana is cheap in water the way it is cheap in money, because it is heavy and fast and grown where it rains.

The dry coasts

Ecuador is the exception that explains the blue water. The coastal plain south of Guayaquil, where the largest plantations are, lies in the rain shadow of the cold Humboldt current, and from June to December it hardly rains; the plantations there are irrigated from the rivers that come down from the Andes and from wells, by sprinklers over the canopy or by furrows between the rows, and the blue share of an Ecuadorian banana is far above the global average. The same is true of the plantations of northern Colombia around Santa Marta, of the Dominican Republic, and of the Canary Islands, where the bananas that supply Spain grow on terraces of volcanic rock on Tenerife and La Palma and are watered from mountain tunnels and, increasingly, from desalination plants, which makes the Canary banana one of the few crops on Earth grown partly on seawater.

The bagging is part of the water story too. The blue bag around every bunch, which is the single most visible thing on a plantation, keeps insects and scarring off the fruit and raises the temperature and the humidity inside it, so that the bunch fills faster; a plantation's bags are changed with every crop and the old plastic, in the countries without a collection scheme, goes into the drains and the rivers that run through the plantations to the sea.

The packing shed

The bunch arrives at the shed on the cable, and the first thing that happens to it is water. The hands are cut from the stalk and dropped into a long tank, where they float for a quarter of an hour while the latex that runs from the cut stems bleeds out, because latex stains the skin; a second tank rinses them; and the clean hands are sorted, labelled and packed into the boxes of eighteen kilograms that the whole trade is built around. The tanks are drained and refilled through the day, and the water that leaves them carries the latex, the field dirt, and a dose of the fungicide that is added to the last rinse to stop the fruit rotting at the crown on the three week voyage. A packing station is a small food factory and its wastewater is the wastewater of one, which the effluent article on this site describes: organic, cloudy, and in most of the growing countries discharged to a ditch.

The planes

The water that the plantations put into the air on purpose is the grey water of the footprint, and it comes from a fungus. Black Sigatoka is a leaf disease that spreads in wet air, which is the air of every banana region, and that cuts the yield of a plantation by half if it is left; the only defence at the scale of an export plantation is fungicide, sprayed from small aircraft over the canopy, and in the wettest regions, in Costa Rica, Panama and the Ecuadorian north, the planes fly forty to sixty times a year. The chemicals drift, onto the workers' housing at the plantation's edge, into the drains and the rivers, and the grey water of the footprint, a few dozen litres per kilogram, is the water needed to dilute what reaches the rivers to a safe level. On the plantations certified by the fair trade and rainforest labels the spraying is done with buffer zones and the drains are planted; on the rest it is not, and the rivers of the banana coasts carry the fungicides to the sea.

One plant

Every banana in the export trade is the same plant. The Cavendish is a clone, grown from shoots, with no seeds and no sex, and every plantation from Ecuador to the Philippines is genetically one individual, which is why the fruit is so uniform and why a disease that can kill one plant can kill them all. It has happened before. Until the 1950s the export banana was a different clone, the Gros Michel, and a soil fungus called Fusarium wilt, or Panama disease, spread through the plantations of Central America and killed it; the Cavendish was the replacement, chosen because that fungus could not touch it. A new strain, tropical race 4, that can touch it appeared in Taiwan in the 1990s, spread through Asia, reached Mozambique and Jordan, and in 2019 was confirmed in Colombia and in 2021 in Peru. It lives in the soil for decades, it travels on boots and tools and in water, and there is no cure; a plantation that has it is finished. The industry's response is quarantine, and breeding, and the search for a successor that the trade can live with. Whatever it is, it will drink the same rain.

The number in context

A banana is about a hundred litres, which is a cup of coffee's water for a whole fruit, and the reason to think about it is the same as for the avocado on this site: the geography matters more than the number. A banana grown on the Caribbean coast of Costa Rica is rain that would have fallen anyway, used by a plant that grows where almost nothing else exports; a banana grown on the dry coast of Ecuador or on a Canary terrace is river water or desalinated water in a place that has little, and the hundred litres means something there. The water that leaves the region in the fruit is a few hundred grams a banana. The rest stayed where it fell, or went back into the air, or down the plantation's drains with whatever the planes left on the leaves.

A hundred litres a banana, a clone from Ecuador to Mindanao, and a fungus in the soil that has crossed the Pacific.