The Butterfly Effect: A Battle Heats Up in the Mosel

The endangered Apollo butterfly in its home on the lower Mosel terraces rests on vegetation with wings unfolded.

One afternoon some 60 years ago, MIT professor Edward Lorenz was running weather simulations in a Cambridge computer lab. He tweaked a single, seemingly negligible variable. The result was a dramatic change in the weather patterns his model predicted. He later likened the effect to a butterfly fluttering its wings and causing a tornado. The “butterfly effect,” as it’s come to be known, now appears to be at work in the Mosel. Naturalists, government officials, and wine growers are suddenly locked in a high-stakes battle over the rights of two endangered species — the Mosel terraces and the Mosel Apollo butterfly. The clock is ticking down on a decision that could have lasting effects on an irreplaceable ecosystem.

“No Going Back”

Late last year, wine growers in the Lower Mosel villages of Winningen, Valwig, and Bremm were informed that the helicopter spraying of fungicides they rely on to fight diseases in their vineyards terraces may soon be banned. This surprise announcement has thrown local growers into crisis. 

“Without pesticides, there is no winegrowing,” say Angelina and Killian Franzen of Weingut Franzen in Bremm, who farm what are reported to be the steepest sites in Europe, referring specifically to the precarious work of wine growing there. “Once viticulture comes to a standstill in these areas, there is no going back.”

The Mosel terraces are among Europe’s most distinctive cultural landscapes. Over centuries, they were hand-built on cliffs and crags, supported by dry stone walls. They are monuments to the work of generations of growers. They remain cost and labor-intensive to maintain and to farm.

But a handful of growers have decided these sacrifices are worthwhile. The terraces give rise to some of Germany’s most distinctive Rieslings: opulent, layered wines that offer a paradoxically generous response to their austere origins. They, too, are cultural treasures.

Riesling vines are prone to outbreaks of oidium (powdery mildew) and peronospora (downy mildew). These fungal diseases are difficult to control and can cause severe crop losses. On less daunting terrain, growers can manage them with sulfur and copper, two treatments approved by the EU for organic farming. But in the terraces, many growers rely on broadcast synthetic fungicides.

Steep vineyard terraces rise above the Mosel river.
Vineyard terraces in Bremm on the Mosel. Photo credit: MaxAdams

Vineyard terraces are singular biotopes. Among the many wild plants, animals, and insects that thrive in the Mosel terraces is the parnassius apollo vinningensis — a rare subspecies of butterfly better known as the Mosel Apollo. (The name vinningensis derives from Winningen, one of the Mosel terraces’ flagship villages.) 

Lepidopterists prize the Mosel Apollo for its large size and striking markings: black and red dots and rings on delicate cream-colored wings. They say that although this butterfly was common in its favored habitats a century ago, most of these have been destroyed. The Apollo now survives in just a handful of places worldwide. The Mosel terraces are one.

The man-made stone walls that support the terraces create ideal conditions for the vegetation the Apollo thrives on. White stonecrop, a drought- and heat-tolerant creeper with small fleshy leaves, is by far the most important food source for the Apollo during its caterpillar phase. Thistles, knapweeds, and wild marjoram also flourish among the dry, sun-soaked stone walls. These, too, nourish the Apollo.

Naturalists Sound the Alarm on the Mosel Apollo

A delicate balance of man-made landscape and wildlife held for generations. But in the 1980s, naturalists sounded the alarm. “The Mosel Apollo was close to extinction,” writes Helge May of Naturschutzbund Deutschland (NABU). The culprits, naturalists claimed, were helicopter-broadcast insecticides. The chemicals were intended to protect vines from insect predators. But, say the naturalists, they killed indiscriminately. 

At the same time, May reports, widespread vineyard reorganization (Flurbereinigung) and a wave of abandonment of the terraces by growers who could no longer afford to maintain them further eroded the Apollo’s habitat. 

Concerned lepidopterists banded together. Vocal organizations succeeded in getting insecticides banned from a large stretch of the Mosel terraces. The Apollo rebounded.

By 2012, there were again reports of a dramatic decline in the Apollo population. The hunt was on for a cause. Changes to local vegetation and climate were considered, but suspicion soon turned to a new fungicide, Fluopyram. This broad-spectrum foliar (leaf-based) treatment came into use around that time.

Although a linkage between Fluopyram and the health of the Apollo has not been proven, concerned naturalists see a potential link. “The population of the Mosel Apollo butterfly is acutely threatened with extinction,” says Charlotte Reutter, of the BUND NRW nature conservation foundation, “also through the use of fungicides by helicopter in the areas where they occur.”

She points to “cocktails of 20 different pesticides” that she says are applied by helicopter to the steep slopes approximately every ten days from mid-May to the end of July. These are “in the immediate vicinity of the butterfly’s habitats.”

Dr. Maximilian Hendgen, who heads the Mosel Winegrowers’ Association and Mittelrhein Winegrowers’ Association, explains that the application of fungicides by aircraft must be approved by the respective federal state (in this case Rhineland-Palatinate) through an annual application process. The approving authority is the Federal Office of Consumer Protection and Food Safety (BVL), which in turn consults two other federal offices, the Julius Kühn Institute and the Federal Environmental Agency (UBA).

As part of the approval procedure for 2024, Hengden notes, Rhineland-Palatinate was requested to draw up a more extensive protection concept, which the state did.

“At the beginning of December,” Hendgen says, “we were informed verbally by the Rhineland-Palatinate Ministry of Viticulture that the UBA had rejected the protection concept … and had spoken out against helicopter approval for 2024. Instead, the UBA considers only the use of drones in the Apollo occurrence areas to be approvable under certain conditions.” 

A sign in German warns of the use of helicpoters to spray synthethic materials during summer months.
Photo credit: Valerie Kathawala

A More Complex Cause?

Ansgar Schmitz, who leads Moselwein e.v., an organization that represents the interests of member growers, acknowledges that the population of the Apollo butterfly has declined in recent years. “The causes have not yet been investigated,” he noted in a late-December statement. “Experts cite hot, dry summers as well as the decline in vineyard area due to rewilding as possible causes.” 

He reports that for years Mosel wine growers have been involved in initiatives to protect the Mosel Apollo and its habitat. He also says that biodiversity studies have shown an array of rare plant and insect species living in these sensitive areas precisely because the steep slopes and dry stone walls afford a unique habitat — despite the use of broadcast fungicides, he notes.

Reinhard Löwenstein of Weingut Heymann-Löwenstein in Winningen, blames the 2012 Mosel Apollo die-off on a hard winter that year. Longer term, he sees the butterfly’s decline correlating with winters that are too humid and warm, and summers that are too dry. 

He is willing to explore the possibility that fungicides could be implicated. But, he points out, the interactions in nature are too complex to allow for easy blame. “Modern methods make it possible to measure to the fourth decimal place the often dubious achievements of civilization. With regard to the Apollo butterfly, however, there are no relevant findings.”

Doom Loop Looms for the Mosel Terraces

Schmitz and the growers his organization represents argue that without helicopter spraying, the vines would succumb to diesase, the terraces would become overgrown, in time the historic stone walls would crumble, and an irreplaceable ecosystem of plants, insects, animals, and humans would collapse.

“The supposed rescue of the Mosel Apollo through a helicopter ban would likely achieve exactly the opposite,” Schmitz says. It would “also jeopardize the existence of numerous wineries that passionately cultivate the wine-growing landscape on the terraced Mosel.” 

Grower Robert Kane of the Madame Flöck winery in Winningen says that “considering the abruptness, unknowable factors, as well as the lack of any other viable option for replacement, [the ban] is extremely cruel and shortsighted to the continuity and community of winemakers and producers of the region.”  

Of the 3,400 hectares of steep slopes on the Mosel, the ban will affect just 60 to 70 hectares. But to growers like Kane, these are the 60 or 70 hectares that matter most. “The most prized and historic vineyards would be significantly, if not entirely, lost,” he says, “This would have hugely negative effects on all wineries regardless of the amount of plots each has in the lost areas.”

The specter of a doom loop looms: Without the wines and the cultural landscape that supports them, the region would lose a powerful draw for tourists — a pillar of the Mosel economy. 

Butterfly effect indeed.

Exploring Alternatives

Immediate solutions appear thin on the ground. It is highly unlikely that sufficient research into possible connections between sprayed fungicides and Mosel Apollo die-off could be conducted before the proposed ban is enacted. 

Mosel terrace growers interviewed for this article say organic alternatives to synthetic fungicides also do not appear to be an option. According to Angelina Franzen, “the only means that can be used in organic viticulture (sulfur and copper) would be subject to the greatest restrictions under the proposed regulation. This is not about soil cultivation (weedkillers or similar) but solely about plant protection products to combat oidium and peronospora.” 

Charlotte Reutter of BUND acknowledges the difficulties fungal diseases present in viticulture and that “even organic viticulture does not yet have the perfect ecological measures” to combat them. 

If aerial fungicides remain in use, there is broad support among conservationists and terrace growers for a switch from helicopters to drones. Drones are smaller, nimbler, and could improve the targeted delivery of fungicides. 

But the Mosel Winegrowers’ Association says that the short notice given by the UBA will make it almost impossible to convert to drone spraying for the 2024 season “due to numerous technical, personnel, and licensing problems.”  

“The drone technology is not ready yet,” says grower Janina Schmitt of Weingut Matterne & Schmitt in Winningen. “We need time to develop and get used to other technologies.”

“Time is pressing for a solution,” the farmers and growers association says. Preparations and approval procedures must begin in January in order to be operational by May. The association notes the possibility of a complete shutdown of any aerial spraying in the terraces this year.

“Terraced vineyards are not a natural landscape, but a landscape created by man over thousands of years,” Löwenstein emphasizes. “If vineyards revert to nature, undergrowth suffocates the unique vineyard flora and fauna within a few years. Our predecessors were confronted with this scenario 170 years ago, when diseases introduced from America almost destroyed viticulture. Salvation came through the development of pesticides. The vines are still dependent on them.”

The future again hangs in the balance, this time on the flap of a wing.

2 February 2024 Postscript

The government of Rheinland Pfalz announced today that a compromise solution would be permitted for 2024.

“We will be able to implement vine protection in the Apollo butterfly areas in 2024 using helicopters and drones,” said regional Viticulture Minister Daniela Schmitt. Growers and companies that perform vineyard spray services will be permitted to start planning the season as early as next week.

The lack of alternatives to sulfur and copper for organic viticulture remains a thorny issue in the Mosel Apollo butterfly habitats. “This area must also be discussed at the EU level in the future, not least with regard to the approval of potassium phosphate,” Schmitt noted, referring to a treatment that had been permitted in the past but has since been excluded from permitted organic vineyard treatments.

A Truce Is Reached

Updated 6 February 2024

A provisional compromise was announced this week by Rheinland Pfalz Viticulture Minister Daniela Schmitt.

“We will be able to implement vine protection in the Apollo butterfly areas in 2024 using helicopters and drones,” Schmitt said in a statement. Accordingly, growers and vineyard spray service companies will be permitted to start planning the 2024 season as early as next week.

Growers reacted with relief tempered by concern.

“First and foremost, we are happy that helicopters can continue to fly for this year,” said Angelina Franzen of Weingut Franzen in Bremm. “Of course, we also want this certainty for the coming years because we invest an incredible amount of time, money, and work in our steep slopes and don’t want to worry every winter about whether this phase of uncertainty will come again.” 

All stakeholders now plan to meet to develop a joint concept. “Let’s just hope that a way can be found together in the future and that we are not presented with a fait accompli,” said Franzen, referring to the abruptly announced ban that triggered growers’ alarm.

Above and beyond the helicopter delivery of plant protection treatments, a lack of alternatives to sulfur and copper for organic viticulture remains a thorny issue. “This area must also be discussed at the EU level in the future, not least with regard to the approval of potassium phosphate,” Schmitt noted, highlighting a fungicide treatment permitted in the past but currently banned from organic vineyard treatments in the EU.

This is an issue that will flutter wings far beyond the Mosel Apollo’s range.

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