Florida Bar Exam 2012 Essays On Global Warming

ACADIA NATIONAL PARK, Maine — With milder winters sparking a surge in deer ticks, park rangers now duct-tape their ankles while combing the wilds of Acadia, where native flowers are disappearing at alarming rates and invasive species are thriving.

Along the rocky coast of Georgetown, Maine, lobstermen are finding more black sea bass in their traps, spiny intruders that until recently were almost never spotted so far north. In a pond in Brunswick, an increasingly prevalent disease has ravaged amphibians.

In a state with the highest percentage of forested land and a long, famously scenic coastline, where timber and fisheries remain at the heart of the economy, climate change has become an immediate concern.

Heat waves, more powerful storms, and rising seas are increasingly transforming Maine — effects that most climate scientists trace to greenhouse gases warming the planet. Wedged between powerful streams of cold and warm air, the state is buffeted by climate fluctuations in the arctic and the Gulf of Maine, both of which are warming rapidly.

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Over the past 100 years, temperatures throughout the Northeast have risen by about 2 degrees Fahrenheit, according to a federal report released this year known as the National Climate Assessment. Precipitation has increased by more than 10 percent, with the worst storms bringing significantly more rain and snow. And sea levels have climbed by a foot. A study by the Gulf of Maine Research Institute this year found that coastal waters are warming at a rate faster than 99 percent of the world’s other oceans.

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Maine, scientists say, is uniquely vulnerable.

“More than any other state, because of its immense natural resources and where it’s located, Maine is particularly sensitive to changes in climate,” said Paul Andrew Mayewski, director of the Climate Change Institute at the University of Maine. “We’re heavily dependent on stability in the environment, but we’re going in the direction of instability. We’re at the beginning of abrupt climate changes.”

The National Climate Assessment’s predictions for the future are grim: Temperatures are projected to continue their rise, up by as much as 10 degrees by the end of the century. Sea levels could increase as much as 4 feet. Storms will likely grow in intensity, while heat-related deaths in a state where much of the population is elderly and lacks air conditioning are expected to climb as well.

Some benefits may come with these trends — a longer growing season, more tourists drawn to the state’s coast and other attractions by generally more temperate weather. And not all experts accept the specifics of the forecast — some call the estimates alarmist; others, too cautious.

But the scientific consensus is growing. Some of Maine’s natural marvels will soon feel the impact of climate change. Or they already have.

Moose are coping with more tick-borne diseases. Puffins are at risk as their prey, such as herring, dwindle and move further north. Lobster and clams are suffering shell disease that has been linked to the acidification of coastal waters.

The warning signs are getting harder to ignore.

Rare disease imperils frogs

In Brunswick last year, Nat Thoreau Wheelwright waded into his backyard pond for a swim and noticed something more disturbing than the usual bounty of slithering leeches.

Thousands upon thousands of tadpoles — clumps of them floating or mired in the bottom murk — had died overnight. “It was like an entire city had been wiped out,” he said.

A day before, Wheelwright, chairman of the biology department at Bowdoin College, had noticed a thriving population of the wood frog tadpoles flitting through the copper water, which he monitors as vigilantly as his namesake observed Walden. He estimated that more than 200,000 tadpoles had died within 21 hours — which would make it the largest, most rapid mass death of amphibians ever reported in academic literature, he said.

Was it a strange but very localized catastrophe, or a kind of alarm bell? Wheelwright set out to find out. He sent several of the bloated tadpoles to colleagues at the University of Tennessee, who confirmed his suspicions through DNA analysis. They had died as the result of ranavirus, a disease that scientists say is a leading reason why 1 in 3 amphibians around the world are at risk of extinction.

It was the second known account of a die-off in Maine associated with ranavirus. The disease has thrived and moved north with the milder winters of recent years and the spread of invasive species, devastation that Wheelwright and colleagues described this summer in the journal Herpetological Review.

Wood frogs are among the most abundant amphibians in North America, so there’s little risk of the species’ extinction anytime soon. But with highly permeable skin that makes them vulnerable to toxins in the environment, amphibians are considered a harbinger of climate change. The mass deaths of amphibians, which have been reported in Asia, Europe, and South America, signal danger to other animals and plants.

“Amphibians are the most imperiled group of animals on the planet and are the sentinels for environmental change,” said Matthew J. Gray, a professor of wildlife ecology at the University of Tennessee in Knoxville and a coauthor of the report.

Ranavirus has been found in vernal pools as far north as New Brunswick, Canada, and there was a report more than a decade ago of a smaller die-off as a result of the disease in Acadia National Park. But the massive number of dead tadpoles that Wheelwright documented in his pond showed for the first time the lethal speed and danger of ranavirus to large populations of amphibians, the ecologists said.

A range of other amphibians continued to thrive through the die-off, including newts, salamanders, and bullfrogs. That suggested the mass death of tadpoles in the pond, which lacks predators such as fish, wasn’t exacerbated by human contamination or some other pathogen, Wheelwright and others said.

“If this is indicative of what’s happening in nature, it’s really concerning,” said Tom Waltzek, co-director of the Aquatic Animal Health Program at the University of Florida in Gainesville, who represents North America on the board of the Global Ranavirus Consortium.

The potential risk goes beyond the immediate die-off: Repeated exposure to ranavirus could have major consequences for a the wider population of a species. In a separate study, Gray found that an exposed population of wood frogs could disappear in as few as five years if its larvae — tadpoles — are subjected to the disease every year.

Derek Yorks, a wildlife biologist at the Maine Department of Inland Fisheries and Wildlife, now sterilizes his shoes and equipment to avoid spreading the disease. He and his colleagues are increasingly hearing about ranavirus in Maine, but he said the effects are hard to track. The dead disappear within hours.

“They get gobbled up or decompose really quickly,” Yorks said.

In Wheelwright’s pond, wood frogs returned this spring, but there were no 1-year-old frogs breeding and fewer tadpoles. But the population, he fears, could eventually wither away entirely — a deeply disturbing prospect for the biologist, who for decades has eagerly anticipated their intense mating calls, which signal the end of the long winter.

“It would be like the world going from color to black and white or from talkies to silent films,” he said. “Unfortunately, it feels like we’re watching the candle burning out.”

Concerns for lobster

On Sheepscot Bay off Georgetown, Jim McMahan prodded his old lobster boat through the smooth waters, methodically lowering a mechanical winch to check on his hundreds of traps.

The 57-year-old lobsterman, who has been hauling up the rusty cages since he was a kid, manages to make a living from the still-plentiful shellfish in local waters. But he has noticed some disturbing trends in recent years.

Nearly every day now, he pulls up scores of lobsters with diseased shells. “Until six or so years ago, we would never see that,” he said between hauls this summer.

State biologists last year reported that the number of lobsters with the mottled, lesioned shells caught in Maine increased fivefold from 2010 to 2012.

Warmer waters promote the bacteria that cause the disease. Moreover, the increasing amount of carbon dioxide in the atmosphere that is absorbed by the warming ocean has produced more carbonic acid, making it harder for lobsters to build their shells and increasing their vulnerability to the bacteria, scientists say.

The lobster catch is, nevertheless, still booming. Last year, the state’s fishermen caught a record $364 million worth of lobster, $22 million more than in 2012, according to the state’s Department of Marine Resources.

The warmer waters have likely benefited lobster growth and propagation in recent years, but scientists worry that as coastal waters continue to heat up, the lobster could follow the path of cod, which thrive in colder waters and are vanishing from the Gulf of Maine. An assessment this summer by the National Oceanic and Atmospheric Administration estimated that the region’s cod have dwindled to as little as 3 percent of what it would take to sustain a healthy population.

Another concern is the arrival of new, aggressive predators from the south.

In recent years, McMahan and other fishermen here have discovered an increasing number of black sea bass in their traps. “We didn’t have any idea what they were when we first started catching them,” said Chris Jamison, McMahan’s deckhand.

The sea bass, which have a distinctive black stripe visible underwater, have been creeping up the coast from their traditional home in the mid-Atlantic. They could prove to be a lucrative market for local fishermen, but they eat a lot of crustaceans, including baby lobsters.

Concerns about the future of lobsters, which account for three-quarters of the value of Maine’s fishery, led McMahan’s daughter, Marissa, a doctoral student in marine sciences at Northeastern University, to base her dissertation on the northward migration of black sea bass.

“They are voracious predators,” she said. “Unlike cod, which are usually deeper and further offshore, sea bass come into shallow, rocky habitats, where there aren’t many predators. It’s the same area where the juvenile lobsters have refuge.”

Over the past few years, she has collected an increasing number of black sea bass that local lobstermen found in their traps, with hopes of better documenting their movement. There is little rigorous data on sea bass in Maine, but scientists are now paying attention to their numbers.

“There is concern that they and other predatory fish from the south could impact the lobster population,” said Andrew J. Pershing, chief scientific officer at the Gulf of Maine Research Institute.

The state has also taken note of the new arrival. Last month for the first time, Maine fishery officials proposed regulations to manage recreational and commercial fishing of black sea bass, allowing a modest catch of nearly 11,000 pounds a year, in hopes of assessing the costs and benefits of the emerging fishery.

At the dock in Georgetown, local lobstermen had mixed feelings about black sea bass, which have brought better prices than lobster in recent years.

“If they take some pressure off the lobster industry, that would be great,” said John Tarbox, 61, while bringing in about 200 pounds of lobster. “I’m not too worried.”

But Libby Nilsen, a wholesaler who buys lobsters at the dock, said she has heard complaints from fishermen further south, where black sea bass are more abundant. “They’re eating all the baby lobster,” she said. “That can’t be good.”

Plant species disappearing

On a balmy morning last month in the woods on Mount Desert Island, Abe Miller-Rushing poked through the bramble until he found a sprawling shrub called Morrow’s honeysuckle, which has been displacing native plants since it arrived from East Asia in the 1800s.

“This is one of the reasons why we’re losing diversity here,” said Miller-Rushing, the science coordinator at Acadia National Park, which now spends more than $200,000 a year to manage all the invasive plants.

Nonnative shrubs and wildflowers such as purple loosestrife, glossy buckthorn, and barberry are spreading in the park, while native flora such as orchids, asters, and lilies are disappearing.

Over the past century, as warmer, wetter weather allows plants from the south to thrive here, about 30 percent of the park’s 500 wildflower species have declined in abundance, and 92 species have disappeared, according to new research.

One study found that native trees such as fir, spruce, aspen, and paper birch — about 16 percent of 83 species of trees in the park — are also facing significant declines or are at risk of disappearing from Acadia. Other trees more common further south, such as hickory and various species of oak and pine, may in time displace them.

With an average year at the park now warmer than all but a few of the hottest years over the past century, with birds like the black-capped chickadee, Maine’s state bird, moving away to the north, and the increasing erosion of its iconic craggy coast, Acadia is experiencing a greater impact from climate change than nearly every other national park, Miller-Rushing said.

“Changes in Acadia are at the extreme end,” he said. “Our forests, coastlines, wildlife, and iconic views are already very different than they were when the park was created 100 years ago, and will change even more in coming years.”

Perhaps the most tangible human impact is a surge in Lyme disease, as more ticks survive the winter. More than a dozen of the park’s 250 rangers have contracted tick-borne diseases in the past five years, Miller-Rushing said, leading rangers to take precautions like taping their pants to their boots.

“This is not glamorous; in fact, it looks downright goofy,” said Anthony Tocci, who oversees management of invasive plants. “But it works.

Last year, Maine saw a record 1,377 diagnosed cases of Lyme disease, up nearly 700 percent from a decade before, according to the Maine Center for Disease Control and Prevention. Other tick-borne diseases, such as anaplasmosis and babesiosis, are proliferating at similarly alarming rates, diagnosed more often as residents become more aware of the diseases.

Officials at the park, which is seeing an average of 8 more inches of annual precipitation than a century ago, said their depleted finances from steep federal budget cuts make it harder to halt the increasing toll of erosion.

Culverts along the park’s historic carriage roads and hiking trails, unable to handle the storm drainage, have led to more washouts and closures. Rising seas are threatening salt marshes as well as 5,000-year-old native American archeological sites called shell middens.

“A huge task for the park is to try . . . to meet increased flows and to try to plan for the unknown — what the future under climate change may look like,” said Rebecca Cole-Will, chief of resource management at Acadia.

For Caitlin McDonough MacKenzie, a doctoral student in biology at Boston University, the park’s threatened future is visible in the present.

Her research has found that plant species are disappearing uniformly throughout the park — in wetlands, grasslands, and forests — and that earlier thaws have allowed shrubs sensitive to temperature, such as Morrow’s honeysuckle, to bloom earlier and displace those that grow on a time cycle.

Last year, she began testing how low-bush blueberries, sheep’s laurel, and three-toothed cinquefoil grow at different elevations on Cadillac Mountain. She has found those at lower elevations, where it’s warmer, are blooming more quickly.

Her ultimate concern is that as plants bloom earlier, they may no longer remain in sync with the bees that pollinate them and could become more susceptible to large die-offs from late frosts.

“With climate change, you can’t just put a fence around it to fix the problem,” she said. “The plants we try to protect may not be able to grow there anymore.”

She worries that in coming decades she won’t recognize the Acadia she knew as a child.

“It’s definitely scary,” she said, then offered her apocalyptic vision. “The park I thought I knew really well isn’t going to exist anymore. It’s going to look more like the Jersey Shore.”

David Abel can be reached at dabel@globe.com. Follow him on Twitter @davabel.

Modelling overview

Our study shows that modelling driven by locality data of sufficient quantity and quality (i.e. 349 unique localities, each accurate to 30 arc seconds resolution (c. 1 km diameter) or less), and conducted on a regional scale, drives robust models for Arabica. This approach appears to outperform environmental envelope methods based on the climatic thresholds of a limited number of variables [14], [15], [36], e.g. mean temperature and mean rainfall. Our predictive present-day distribution model for Arabica is assumed to be accurate and robust (Figures 1 and 2), due the strength of the distribution model and robust agreement with both ground-truthing and visual assessment using satellite imagery (using Google Earth (Version 5; ©2010 Google). We infer that Mt. Marsabit in northern Kenya is probably not part of the natural range of Arabica, due to the low prediction scores for this locality. This assumption supports the available molecular data, which shows that samples (two in total) from Mt. Marsabit fall within a broad selection of Arabica cultivars and are not aligned with spontaneous populations from Ethiopia [23]. Further work on this outlying locality is required, including fieldwork in those areas that receive slightly higher predictions (see Results – Model of historical and present-day distribution.)

Future distribution predictions for indigenous Arabica based on future scenarios (B2A, A2A, A1B) and the HadCM3 climate model [52], [53] for the time intervals 2020 (an average of the years 2010–2029), 2050 (2040–2059), and 2080 (2070–2089), were analysed using a locality analysis and an area analysis. Both analyses performed well but overall the locality analysis has greater meaning and more practical applications: the data (actual localities based on in situ observations across the distribution range) can be tracked through time, from 2020 to 2080. Generally, the locality analysis also requires fewer assumptions. In the area analysis, the 68% (optimal) threshold is likely to be very exclusive. For example, if in 2050 a pixel falls into the 95% (intermediate) threshold from the 68% threshold it would stay within the former threshold in subsequent dates. This same exclusivity is present in the 95% (intermediate) threshold, but to a lesser degree; it does not apply to the 100% (marginal) threshold. The exclusivity of the area analysis means that more caution is required in the interpretation of the predictions. Moreover, in the area analysis the actual area of change is not entirely meaningful, even when surface area values are provided, because of the clipping of the study area and other assumptions made in the modelling. What is important is the relative change across time and scenarios, i.e. the universal reduction of available suitable bioclimatic space until 2080 (Figure 6).

Our modelling approach for Arabica is not constrained by climatic optima, as used in environmental envelope methods [14], [15], [36], and by default encompasses the broader bioclimatic ranges encountered in wild populations, which have a much higher genetic diversity and a greater physiologically variability compared to cultivated Arabica [28], [29]. It is also clear that there is a dichotomy between modelling the success of plantations, which is largely measured by yield and beverage quality [3], [5] and the health and survival of the species, which in stressed environments may exceed the given climatic optima required for successful production of Arabica coffee beans. For example, temperatures above 28–30°C are likely to reduce flower bud formation (and thus fruit production) in indigenous Arabica populations but may not significantly influence morbidity or mortality, at least in the short term (A.Davis and T.Gole, pers. observ.).

Bioclimatic suitability for indigenous Arabica is not a simple association with a linear temperature change but is heavily influenced by seasonality (as identified above). This issue is further complicated by two other factors. Firstly, the present-day prediction (the year 2000) is actually an accumulation of collection dates from 1941–2006 and secondly, the climate data used for the modelling for the year 2000 is accumulated from weather station data from the 1961s to 1990 [49]. The consequence of these considerations is that the prediction for the present-day (2000) distribution of wild Arabica (Figures 1 and 2) could be overly inclusive, that is, the area predicted could be larger than it actually is. However, examination of suitable vegetation and optimal bioclimatic area, based on field observation (S. Demissew, pers. comm.; I. Friis, pers. comm.; T. Gole and A.Davis, pers. observ.) and inspection of satellite imagery shows that this is not the case: the predicted distribution for indigenous Arabica is concurrent with known populations and areas that are highly suitable for the occurrence of this species.

Implications for wild populations of Arabica coffee

Our modelling shows a profoundly negative trend for the future distribution of indigenous Arabica coffee under the influence of accelerated global climate change. In our locality analysis the most favourable (and most conservative) outcome (scenario B2A; all thresholds) would be a c. 65% reduction in the number of bioclimatically suitable localities, and at worst (scenarios A2A, A1B; 68% threshold) an almost 100% reduction, by the year 2080 (Table 1; Figures 3 and 4). Part of the strength of this analysis is that the locality data used for the modelling covers a high proportion of suitable bioclimatic space in remaining areas of Moist Evergreen Afromontane Forest and Transitional Rain Forest [56], i.e. the vegetation types where Arabica exists. Even if new localities for Arabica are recorded, these are likely to represent a small proportion of those already known, based on the few remaining suitable areas for which we do not have occurrence records. New records are unlikely to influence the modelling, as performed here, to any considerable extent: the predicted percentage loss is unlikely to change dramatically. It should reiterated that our modelling does not incorporate vegetation, due to the absence of a suitable atlas of remaining vegetation for the study area [56]. The assumptions we have made, post modelling, are based on intact vegetation, and on the highly unrealistic premise that there will be negligible human generated land-use change until 2080. Therefore, all of our future predictions should be considered as moderate, at the very least.

In our area analysis, the most favourable outcome (scenario B2A; 100% (marginal) and including all other thresholds) would be a 38% reduction in suitable bioclimatic space, and the least favourable (scenarios A2A, A1B; 68% (optimal) threshold) a 90% reduction, by 2080. The area analysis predicts a general northward concentration through time, i.e. an increase in suitable bioclimatic space in the northern part of the distribution, although the likelihood of migration and establishment by Arabica is assumed to be extremely limited based on insubstantial dispersal and colonization ability, especially in stressed environments. Arabica has a relatively long generation time: even in cultivation it requires a minimum of three to four years to produce fruit and at least five to eight years to reach maximum reproductive potential [60]. Re-colonization potential into suitable areas, let alone marginally suitable ones, is restricted even at the simplest level (e.g. without considering pollinator and dispersal availability, de-forestation, loss of niches to more aggressive colonizers). At best re-colonization will be limited and localized, especially with increasing distance from the parent population. Moreover, it is doubtful that suitable vegetation types will have established within the time-frame required. Totally unsuitable habitat (e.g. Combretum-Terminalia Woodland and Wooded Grassland) is highly unlikely to become suitable habitat (Moist Evergreen Afromontane Forest, and Transitional Rain Forest [56]) over an 80 year time period. In our methodology we have imposed a zero rate for migration, based on a neutral colonization rate, an assumption that is supported by studies of other forest dwelling plants, where migration rates to newly formed areas of suitable vegetation are given as either nearly impossible [61]–[63] or severely restricted [64]. Birds are probably the main dispersal agents of coffee species in Africa, but modelling indicates that the avian fauna of tropical regions will be reduced in extent and diversity throughout the century [65], and this is likely to reduce the number of possible dispersal events for Arabica. A further compounding factor is that the present coverage of Moist Evergreen Afromontane Forest and Transitional Rain Forest of Ethiopia, the vegetation housing wild populations of Arabica in Ethiopia and South Sudan, is now fragmented, and often degraded [56]. Fragmentation reduces the progress and success of migration for many forest species, and would hinder the establishment of new areas corresponding to Moist Evergreen Afromontane Forest and Transitional Rain Forest vegetation types. Managed relocation of Arabica individuals or even populations by human effort is conceivable, although as with any other form of dispersal a suitable habitat would have to be available during this process and these may be limited (see above) and localized.

In both the locality and area analysis numerous populations outside the main area of distribution (i.e. SW Ethiopia) are predicted to occur outside of all suitable bioclimatic space for Arabica by 2080 (Figures 4 and 5). Even by 2020, some of the populations on the outer edges of the main SW Ethiopia distribution area, several in the Bale Mountains (southern central Ethiopia), and all populations on the Boma Plateau in South Sudan and Mt Marsabit in northern Kenya, will be occurring in unsuitable bioclimatic space. Bioclimatic unsuitability would place populations in high peril, leading to severe stress and a high risk of extinction in the short-term. Ground-truthing would be necessary to test the likelihood and scaling of predictions in terms of population persistence and survival. A recent survey (April 2012) on the Boma Plateau (A.Davis, T. Schilling, S.Krishnan, pers. observ.) is consistent with our modelling. Observations made in the most suitable bioclimatic space on the Boma Plateau indicated that Arabica populations are stressed (loss of aged individuals, meagre population density, minimal seedling recruitment, low-ratio of flower bud development) compared to 70 years ago [37]; subcanopy ambient air temperatures recorded at the end of the dry season (9–12 April 2012), during the middle of the day, were between 28–30°. Some of this stress has no doubt been caused by human intervention, and probably foremost among these would be the burning of the surrounding Combretum-Terminalia Woodland and Wooded Grassland for grazing, which increases the temperature and lowers the humidity inside the contiguous Transitional Rain Forest. In some places the fire had encroached into the margins of the forest, as demonstrated by the presence of recent charcoal layers detected directly underneath the forest leaf-litter, and this may be expected anywhere where forest and fire-managed grassland co-exist.

There could be a buffer influence for wild populations of Arabica, because the forest micro-environment itself is not included in recorded climate data and therefore not modelled. That is, certain variables such as the mean temperature(s) will be lower inside the forest than in exposed areas in the same general bioclimatic space. In addition, the long generation time of Arabica (c. 50 years, and perhaps up to 100 years [4]) will mean that even if reproduction, dispersal and colonization are reduced, or neutralized, individual trees may persist for some time. However, observations of Arabica populations in South Sudan show that in degraded forest with good canopy cover, at the end of dry season, the difference in ambient air temperature between forest and non forest may only differ by 1°C or less; and on comparing anecdotal accounts with historical records [37] it seems that the mature trees have fared less favourably in these stressed environments compared to juveniles ones (A.Davis, T.Schilling, S.Krishnan, pers. observ.). Moreover, the influences of climate change on the cornerstone species of the Moist Evergreen Afromontane Forest, and Transitional Rain Forest vegetation types are unknown, and thus the outcome for the forest itself cannot yet be predicted.

The impact of multiple compounding influences acting simultaneously on an organism and its associated biota under accelerated climate change would be very difficult to model, but the individual and combined consequence are likely to be negative. The single most important compounding influence for Arabica is almost certainly habitat degradation and loss due to forest modification and clearance, especially for agriculture [4], [17]. This would include the vegetation surrounding and buffering the Moist Evergreen Afromontane Forest and Transitional Rain Forest, i.e. mostly Combretum-Terminalia Woodland and Wooded Grassland but also Dry Evergreen Afromontane Forest [56]. In particular, Combretum-Terminalia Woodland and Wooded Grassland is burnt to produce grazing lands [56] and this in turn can raise temperatures and decrease humidity within Moist Evergreen Afromontane Forest and Transitional Rain Forest, and especially in smaller forest fragments.

Pests and diseases are also likely to be important. A study on the East African Kihansi coffee (C. kihansiensis A.P. Davis & Mvungi) [66], a species entirely restricted to Kihansi Gorge in Tanzania, provides us with a good example of how coffee species are influenced by pests under accelerated climate change. The underground diversion of the Kihansi River for hydropower production was completed in 1999. The mean temperature and relative humidity at this site in 1997 were 21.23°C and 76.64%, respectively; six years after dam construction these had changed to 24.08°C (+2.84°C) and 68.76% (−7.88%) [67]. These changes coincided with the appearance and chronic spread of a parasitic infestation, apparently correlated to the change in local climate, which has seriously undermined the growth and reproductive potential of this coffee species, with severe consequences for the long-term survival of the species [67]. For Arabica, the coffee berry borer (Hypothenemus hampei (Ferrari) [Coleoptera]) poses a significant compounding threat to indigenous populations and plantations. Coffee berry borer, the most important biotic constraint for commercial coffee bean yield worldwide, was unable to complete a single generation per year in SW Ethiopia (Jimma) before 1984, due to low temperatures, but thereafter, because of rising temperatures in the area, it was predicted that the pest would be able to complete one or two generations per year/coffee season [13], [68]. These predictions have been confirmed by an independent study, which shows that the coffee berry borer is now widespread in SW Ethiopia [69]; before 1984 it was absent. Overall, the climatic suitability for coffee berry borer is predicted to increase in southwest Ethiopia [13].

Implications for cultivated Arabica coffee in Ethiopia and world-wide

The outcome of climate change for Arabica cultivation in Ethiopia, the only coffee grown in the country, is also assumed to be profoundly negative, as natural populations, forest coffee (semi-domesticated) and even plantations occur in the same general bioclimatic space as indigenous Arabica. Forest coffee and semi-forest coffee production systems account for c. 25% of total coffee production in Ethiopia [4]. Production is likely to decrease significantly in certain areas, and especially in locations that are presently marginally suitable for coffee production. Most coffee cultivation in Ethiopia is shade-grown and without irrigation, the latter being a practice that can significantly influence the productivity and survival of Arabica in suboptimal growing areas [60]. Unlike native forests, however, there may be greater short term incentives to employ mitigation measures, such as irrigation, particularly at the lower scales involved (e.g. at farm-level).

Our results provide independent validation that Arabica is a climate sensitive species, supporting data on recorded climate optima [3]–[6], results based on environmental envelope methodologies [14], [15], and anecdotal information from coffee farmers. The logical conclusion is that Arabica coffee production is, and will continue to be, strongly influenced by accelerated climate change, and that in most cases the outcome will be negative for the coffee industry. Optimum cultivation requirements are likely to become increasingly difficult to achieve in many pre-existing coffee growing areas, leading to a reduction in productivity, increased and intensified management (e.g. the use of irrigation), and crop failure (some areas becoming unsuitable for Arabica cultivation). Detailed modelling of Arabica cultivation is required, on local and regional scales, in order to inform famers and decision makers as to the requirements for future-proofing the sustainability of their crop. The methodology used here could be adapted for coffee plantations on a regional scale, by substituting the location of plantations for indigenous populations, and by applying a modified threshold approach based on the parameters encountered and employed in cultivation.

Conservation of wild Arabica coffee

Unlike cultivated Arabica coffee, the distribution of indigenous populations is controlled almost entirely by natural, biotic parameters, even though these factors are influenced by anthropogenic actions. Assisted migration of wild Arabica could be suggested as a possible means of mitigation, but in reality this option is laden with constraints. Not least are the short-term financial implications associated with resourcing a medium- to long-term and diffuse (i.e. involving multiple populations) action of assisted migration. Re-locating coffee plantations is likely to bring economic benefits within a realistic time frame; the assisted migration of natural populations of Arabica coffee is not.

What we have shown here is that under a range of emission scenarios some populations of Arabica (occurring in optimal bioclimatic space) might be able to resist climate change until 2080, at least in the absence of severely negative influences (e.g. deforestation). We define these populations here as ‘core localities’ (Figure 7; high prediction totals across all scenarios) and suggest that they should be assessed as candidates for the long-term in situ conservation of Arabica in the face of accelerated climate change. Examination of the main protected areas of Ethiopia shows that some of the ‘core localities’ already fall within those established protected areas [70] and have a reasonable to good degree of protection (e.g. national parks and UNESCO biosphere reserves), although many do not (Figure 7). Where there is a specific objective for the in situ conservation of indigenous populations of Arabica, such as the Yayu and Kafa Biosphere Reserves (Figure 7

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