|Above: A severely depleted Victoria Falls on November 13, 2019. Image credit: Zinyange Auntony/AFP/Getty Images.|
The massive curtain of water in southern Africa between Zambia and Zimbabwe known as Victoria Falls is the world’s biggest waterfall sequence when you take into account both width and height. Often ranked as one of the seven wonders of the natural world, the falls are a prime tourist destination, which explains much of the horrified reaction the last few days as news spread that the falls had dried to a virtual trickle.
Much of the coverage has centered on claims that the region is experiencing its worst drought in a century. The Zambezi River Basin that surrounds and nurtures the falls is a drought-prone place, a semiarid region accustomed to big year-to-year variations in rainfall. It’s typical for the falls to become starkly depleted in October and November, just before the onset of the summer wet season. Pictures of the falls as a raging torrent are more likely taken in March or April.
|Figure 1. Victoria Falls at full discharge on April 26, 2017. Image credit: Kaitano Dube.|
Oddly enough, there’s been no significant long-term decrease in annual average rainfall in the Zambezi Basin.
What’s happened this year is partially a story of a lack of rain—but just as much, it’s a tale of increased landscape-parching heat, combined with an increasingly delayed start to the region’s wet season. Both of these are long-term trends squarely in line with climate change, and they’re also frighteningly consistent with things happening on the other side of the world.
To get the inside scoop on what’s happening in Victoria Falls, I turned to someone who’s been studying the situation closely. Kaitano Dube is a lecturer in ecotourism management at Vaal University of Technology in South Africa. He completed a doctoral thesis in environmental management last year with the title “Tourism And Climate Change: An Investigation Of The Two-Way Linkages For The Victoria Falls Resort, Zimbabwe.” It’s a fascinating case study on how long-term climate change fueled in part by world travel can threaten the viability of a famed tourist site that relies on such travel to thrive.
In Dube’s words, the tourism that buoys the region is both “a victim and a vector” of climate change.
|Figure 2. An aerial view taken on June 29, 2018, shows the site of the Victoria Falls on the Zambezi River at the border between Zambia and Zimbabwe. Image credit: Zinyange Auntony/AFP/Getty Images.|
The spectre of hot drought
The scope of Victoria Falls is breathtaking. Known locally for centuries as “The Smoke that Thunders”, the falls are more than a mile wide (1708 meters) and the height of a 30-story building (108 meters). They include a sequence of six gorges, but most photos are taken where the Zambezi River hurtles over the First Gorge. When the river is running at full tilt in late summer and early autumn, the falls are encompassed by a sea of mist.
Dube set out to study the landmark from several points of view: Is there evidence that climate change is affecting the falls? How can greenhouse emissions from local tourism be reduced? And how do people view these interlinked problems?
Dube drew on 40 years of data (1976-2017) from two observing sites: Victoria Falls International Airport, on the Zimbabwean side, and Livingstone International Airport, across the river on the Zambian side and about 25 miles (40 km) upstream. Both sites have annual rainfall in the neighborhood of 23-27 inches, roughly the same as Sacramento and San Francisco. As with these two cities, there’s major year-to-year variability in how much rain falls; unlike these cities, most of the rain falls in the warm season (which runs from October to April at Victoria Falls).
While there’s been a slight drop in rainfall at the Livingstone site, Dube found no statistically significant changes over the 40-year period. There are extreme swings in rainfall, though, along with a disappearance of the wettest years and a turn toward multiyear drought over the last decade.
|Figure 3. Total annual rainfall at Victoria Falls and Livingstone airports, 1976-2016. Image credit: Kaitano Dube.|
The most dramatic signals of a changing climate at Victoria Falls don’t emerge until you pull back the curtain and look at monthly trends.
In October and November, average rainfall has decreased at a startling rate. Back in the 1970s and 1980s, Victoria Falls got at least 2 in (50 mm) of rain about every other October. Since 2000, the two wettest Octobers (2006 and 2010) produced only about half that amount. After an especially hot, dry summer, river flow at Victoria Falls in the last few weeks has dropped below the 45-year record low set in 1995, according to Dube. Water levels at the Kariba Dam have dropped to their lowest levels since 1996.
|Figure 4. Trends in October rainfall at Victoria Falls (left, 1064 m elevation) and Livingstone (right, 986 m elevation) from 1976 to 2016. Livingstone is about 25 miles upstream from Victoria Falls. Image credit: Kaitano Dube.|
Since there’s been little change in rainfall toward the end of the wet season, the bottom line is that the dry season is getting longer—and hotter. As the low-latitude southern sun intensifies from September to November, it’s capable of baking the landscape if summer rains haven’t yet arrived. At Victoria Falls, the average daily highs in October warmed by a startling 6.8°F (3.8°C) in the four-decade study period, rising from 89.8°F (32.1°C) to 96.6°F (35.9°C). A similar rise was observed at the slightly warmer Livingstone station.
“The temperature increase is way above current projections and models over the same period for the entire world and the region in question,” noted Dube.
|Figure 5. Trends in daily maximum temperature during October at Victoria Falls (left) and Livingstone (right) from 1976 to 2016. Image credit: Kaitano Dube.|
Although the climate of California is starkly different than that of Zimbabwe and Zambia, there’s a noteworthy parallel between the “hot drought” phenomenon emerging in both locations. There’s no long-term trend in annual precipitation for California, but state temperatures have risen about 2°F (1°C) in the last century. Recent delays in the onset of winter rains in California—following intensely hot, landscape-dessicating summers—have opened the door to devastating wildfires, including the most destructive and deadliest on record (the Camp Fire in November 2018) and the second largest (the Thomas Fire in December 2017). And a 2018 study led by Daniel Swain (University of California, Los Angeles/National Center for Atmospheric Research) found evidence in a large climate-model ensemble that the wet season will grow even more compressed in the coming decades, with increased year-to-year “whiplash” to boot.
|Figure 6. Kaitano Dube at the 2019 African Climate Risks Conference in Addis Ababa, Ethiopia, on October 7, 2019. Image credit: IISD/ENB | Kiara Worth.|
Dube is keenly interested in how Victoria Falls will navigate the twin challenges of more-uncertain water flow and the impacts of climate change on tourism. He’s found that business operators and visitors are already noticing changes. A period of extremely low water flow at the falls in late 2015, similar to this year’s trickle, triggered its own rush of concern in social media.
“Tourists complained in the recent past that the water was running very low at the resort at Victoria Falls, which led to a social media outcry in the 2015 and 2016 rainfall seasons as a consequence of extreme [El Niño–induced] drought in the Zambezi Basin,” Dube reported in a 2018 paper for Environmental Society and Policy. “It is important to note that, although there has been a slight increase in rainfall activity in some months particularly in the last 10 years in Livingstone, there is growing concern that the water flow is quickly dropping to unprecedented low levels in October and November.”
In his thesis, Dube peered into the future: “What is worrying from the emerging trend is that there is a real chance that in the long run reduced water levels may result in the change from the Victoria Falls becoming a perennial attraction to a seasonal attraction.” He foresees the potential for a rush of “last chance tourism,” a phenomenon already seen at locations ranging from Mt. Kilimanjaro to the Great Barrier Reef.
|Figure 7. A trader staffing a curio stall assists a tourist in choosing souvenirs on June 29, 2018 in the resort town of Victoria Falls. After nearly two decades in the doldrums, Zimbabwe's tourism sector was enjoying a rebound in 2018. Image credit: Zinyange Auntony/AFP/Getty Images.|
In a 2019 paper for Environment, Development and Sustainability, Dube warned: “Even with the best technology and newer fuel-efficient aircraft on the market, the carbon emissions from the African aviation sector are likely to balloon in the foreseeable future in line with the global trend.”
While there’s no easy way to avoid the carbon footprint of long-distance travel from other continents to Victoria Falls, Dube recommends the region adopt an eco-conscious approach to tourism, one that is reinforced by bringing climate change into the curriculum of economic and tourism development programs at universities. Victoria Falls itself may need to change its approach to tourism with the climate, such as emphasizing what can be done during the low-flow season. “White water rafting and swimming in the devil’s pool are some of the hallmark water activities that can be done during low flow season,” he said in an email. Such times are also good for taking photos of the gorge itself when it’s not mist-enshrouded, he adds.
Overall, said Dube, “The scare of the drying up of Victoria Falls is a stark reminder on the urgent need to tackle climate change. The biggest losers are developing countries and the poorest of the poor.”