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Climate mapping can point to danger spots where new pest threatens Africa’s cycads

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Cycads, the world’s oldest seed-producing plants, are facing extinction. Africa is home to a variety of cycad species and South Africa is regarded as a global hotspot for cycad diversity.

One of the most prominent cycad taxa, the genus Encephalartos, is endemic to Africa and is categorised as “critically endangered” by the International Union for Conservation of Nature. This status indicates that if no conservation actions are taken, it may be wiped off this earth in the near future.

The poaching of wild cycads is the biggest threat to their survival in Africa, particularly the cutting of old trees that are growing in the wild, as they are in high demand in traditional medicine markets and as ornamental plants in gardens. Already, poaching activities in South Africa have resulted in the extinction of three species in the wild.

Now to worsen the scenario, an invasive alien species, Aulacaspis yasumatsui, has entered South Africa. Aulacaspis yasumatsui is a scale insect, commonly known as the Cycas Aulacaspis Scale. It has the potential to kill a cycad plant within a few months after infesting it.

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This insect pest is native to South East Asia. Due to global horticultural trade, it started spreading across the world, posing a threat to the cycad’s existence. This pest has a high potential to spread rapidly across the regions. Controlling it is difficult, costly and labour-intensive once it’s widespread. This is because it forms dense populations preventing the penetration of insecticides.

In the case of a Cycas Aulacaspis Scale outbreak, destroying all cycads in the vicinity is sometimes the only option. Therefore early detection and employing the right management practices are the keys to limiting its further spread, especially in newly invaded areas.

We’ve mapped the regions in South Africa where this pest might flourish. This data can aid conservation enthusiasts, researchers and horticulturalists to monitor and initiate appropriate action when the Cycas Aulacaspis Scale insect is observed. We looked for the potential areas for pest establishment under present and future climate scenarios.

How we did it

Climate plays a significant role in influencing the spread and establishment of invasive alien species in novel habitats. So we used CLIMEX, a bio-climatic software, to map the areas with favourable climatic conditions for the establishment of the pest in Africa. The software uses historical climate data sets and future climate scenarios based on the Intergovernmental Panel on Climate Change recommendations. We focused in particular on likely areas in South Africa, as this pest has recently been reported in the country.

A white-bellied sunbird on a cycad leaf.

A white-bellied sunbird on a cycad leaf in South Africa. Shutterstock/ Johnathan Hollard

We gathered information about temperature, relative humidity, phenology and soil moisture that aids establishment of Cycas Aulacaspis Scale in a novel range. These values were fed to the software, which subsequently predicted potential hot spots for Cycas Aulacaspis Scale establishment.

We then adjusted some parameters to cover all the regions where the insect has already been reported. Once it matched, we ran the model for present and future climatic scenarios in Africa – with a focus on South Africa – to understand potential future distribution.

Is Africa at a higher risk?

Our results showed that all 17 African countries with indigenous Encephalartos cycad species were suitable for Cycas Aulacaspis Scale establishment. The Democratic Republic of Congo, followed by the other central African countries with humid tropical climates, the eastern parts of Madagascar and the east coast of South Africa are highly favourable for the pest’s establishment. In South Africa, parts of the winter rainfall areas and the temperate summer rainfall areas are potentially suitable for this pest insect.

Future climate scenarios were less favourable in South Africa for pest establishment except for the western parts of the Kwazulu-Natal province. This area remains favourable due to favourable temperature and atmospheric humidity throughout the year. Similarly, five other African countries become completely unfavourable under climate change predictions for the year 2100 due to increase in atmospheric temperature, which adversely affects the pest’s growth and development.

But the pest can keep pace with the changing climate. It grows faster and completes more generations per year in areas that will become less suitable or even marginally suitable. This is bad news for cycads.

Going forward

Prevention is better than cure. Where it’s already present, it should be detected early and the response should be rapid. Integrated Pest Management approaches comprising of cultural, biological as well as chemical practices will help in protecting cycads from Cycas Aulacaspis Scale attacks. For example, taking precautions such as chemical sprays at the early stage of an invasion is key to limit further spread.

Furthermore, close monitoring of cycad trade and strict quarantine measures should be implemented in areas where the pest has been recorded. Similarly, close monitoring of the cycad in areas yet uninfected but climatically suitable is crucial. Legislation could aid in preventing further introduction of this pest and reduce the spread.

Many parts of South Africa possess a favourable climate for growth and development of the Cycas Aulacaspis Scale, and it’s already been reported in two provinces. Because it could pose such a severe threat to endemic cycad species in South Africa it warrants receiving high priority from government funded invasive species control programmes.

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Brown locusts have survived a long drought in South Africa – here’s how

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The Northern Cape and Eastern Cape provinces of South Africa recently experienced their longest drought in 100 years. The seven year drought, starting with lack of rains in February 2013, wrought havoc on this sheep farming community. When the summer rains finally fell in October 2020 the farmers had to contend with a locust outbreak as well.

The brown locust found in this area mainly eats grass but will consume any green plants and has been known to decimate maize fields.

The two provinces fall within the Nama Karoo, a vast, open, arid region dominated by low-shrub vegetation. The last locust outbreak in the region was in 2012, so the interesting question is how the insects survived a long drought and could still produce the large numbers seen in the area after the rain.

The answer lies in the fact that the eggs can survive for several years in the soil with the embryos developing at different rates in response to environmental conditions.

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The brown locust (Locustana pardalina) is an arid adapted locust endemic to South Africa. It is a different species to the swarming locusts found in other parts of Africa. It has regular outbreaks in the Nama Karoo region and these outbreaks can extend into the southern parts of neighbouring Namibia and Botswana.

 

The female locust lays on average 380 eggs during her life in 6–10 egg pods. The eggs are protected by being in the soil and by having a foam cap. These drought resistant eggs will remain in the soil until they get sufficient moisture to hatch. Each egg contains an embryo which will ultimately emerge as a hopper.

As a study I conducted has shown, the development of the embryo is complex. In some eggs, there’s a delay in the embryo development regardless of the moisture available, whereas in other eggs the embryo will start development as soon as moisture is available. Both types of eggs can be found in the same egg pod. All embryos, from both egg types, can reduce their rate of development when environmental conditions are unfavourable.

Egg build-up and synchronized hatching

Thus, these eggs can remain in the soil for several years with the embryos waiting to receive sufficient moisture to complete development. This results in synchronised hatching when there’s sufficient rain as all the embryos are at the same stage of development regardless of when the eggs were deposited.

The solitary females tend to lay their eggs in the same areas and thus there is a build-up of eggs in particular areas. How the females find these egg laying sites is unknown. Many farmers know where the potential sites of the eggs are due to the large numbers of hoppers they see emerging simultaneously. But ploughing egg beds to destroy the eggs is not feasible because this also destroys grazing.

While many of the eggs remain in the soil, some hatch and produce the solitary form of the locust, thus maintaining the locust population at a low level. This contributes to the build-up of eggs. With the onset of good summer rains, synchronised hatching occurs along with the growth of grass.

Grass found in the region, Enneapogon desvauxii, has long-lived seeds which germinate with the onset of rain, providing food for the hoppers. A pheromone (or chemical) found in locust faeces stimulates the hoppers to aggregate and develop into the gregarious phase if the population density is high. These hoppers form bands and move up to 8km per day in search of food, competing with livestock for the available grazing.

The behaviour of the adults depends on the hoppers. If the hoppers don’t form large enough bands and change colour from green/brown to black and red/orange, then the adult will not form into large swarms and leave the area. As is currently happening in the region, the adult swarms are smallish, locusts fly close to the ground and tend to stay in the same area. Without control these adults will mate and lay eggs, adding to the build-up of eggs in the area.

Due to the large area and sparse human population many swarms aren’t detected. When they are, locust control district officers in each region co-ordinate the chemical control – spraying the government approved insecticide with knapsack and vehicle pump sprayers. The hoppers are sprayed while they roost on the bushes, either in the late afternoon or early morning. The adult swarms are sprayed while they are settled on a field for the night. This targeted spraying is less environmentally damaging than aerial spraying.

Going forward

Alternatives to the environmentally damaging chemical control are needed because even though there has been over a century of chemical control, the locust outbreaks still occur. Future research needs to focus on understanding the impact of rangeland management and climate change on locust outbreaks.

Location of the egg laying sites and criteria used by female locusts in choosing these sites will improve the current prediction models and assist in locust surveillance.

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Why the fire on Cape Town’s iconic Table Mountain was particularly devastating

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The devastating fire that ran its course across the side of Table Mountain in Cape Town this week has put the spotlight back on the management of an iconic range that’s home to some of the most biodiverse vegetation in the world. And what should – and could – have been done to reduce the risk of a catastrophe that destroyed priceless cultural heritage.

Table Mountain National Park is clothed in fynbos – a distinctive type of vegetation found only in South Africa – and is surrounded by the city of Cape Town.

Fynbos is a highly flammable shrubland, which has evolved over millennia to become dependent on fire for survival. It burns. Science tells us that we can expect most fynbos to burn on average every 12 to 15 years in natural conditions.

Therefore managing fynbos means managing fires.

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Fire hazard is influenced by three factors: the weather, an ignition source and fuel loads.

The weather can affect fires by increasing spread through high wind speeds or resulting in dry vegetation after a period of warm weather. Ignition sources may be a result of lightning or arson.

Both weather and ignition sources are hard to control and prevent, and yet often receive the most media attention. But the one factor that is possible to manage, is fuel loads. Fuel loads in fynbos can be kept down through ecological burns and keeping the mountain clear of invasive alien trees.

The recent out-of-control wildfire on Table Mountain may be linked to several key issues: fire suppression, alien trees, constrained budgets and unsupportive policies, together creating a wicked problem. Climate change may also have played a role in the high temperatures and fierce winds around the time of the fire, though attribution studies will need to confirm this.

Fire suppression

Recent research has shown that urban expansion of Cape Town has created anthropogenic fire shadows which are changing the fire regime, often causing a decline in fire activity. For example, the fires that used to sweep the slopes of Newlands and Kirstenbosch from the flats below have been blocked by the suburbs of Newlands and Rondebosch, meaning that the fynbos on these slopes has not burnt in decades.

Scientists are calling this process a “hidden collapse”, that desperately requires management intervention. They also predicted two years ago that this would lead to extreme fires in ecosystems globally where there was no ecological restoration and where fuels were allowed to accumulate.

Further evidence of a decline in fire activity in Table Mountain Natonal Park is presented in a study on indigenous forests which showed that they had been expanding on Table Mountain due to fire suppression policies.

Invasion of alien trees

Invasion of alien trees also contributes to increased fuel loads, and therefore more dangerous fires. Fynbos is made up mainly of shrubs and therefore when alien trees invade or are planted in fynbos, they tower several meters above fynbos, carrying considerably more fuel. A change from fynbos to pines and gum trees can increase fuel loads from 4 to 20 tonnes per hectare.

One study found that the 2017 Knysna wildfire had a significantly higher severity in plantations of invasive alien trees and fynbos invaded by these trees, compared to areas with just fynbos.

Unfortunately, invasive alien plant species are proliferating faster than authorities can remove or manage them. This is also despite the efforts of Working for Water Teams working in the park, as well as over 20 volunteer groups working hard to clear invasive alien plants on the Cape Peninsula and beyond.

In an article in 2019, scientists warned of the areas of highest risk at the urban-fynbos fringe, and gave clear steps that could be taken to mitigate this risk. But these issues have been identified as early as 1995.

Could Cape Town have been better prepared to deal with this disaster?

Why is this a wicked problem?

Although we have the ecological knowledge to undertake prescribed burns and alien clearing, unsupportive policies, constrained budgets and a complex social setting make implementation challenging.

In the 1970s and 1980s, regular prescribed burns were practised in some parts of the park  with the dual goals of rejuvenating the fynbos, and reducing fuel loads (and hence risk). However this was halted at the end of the 1980s, and fire management shifted to fire suppression to protect plantations and residential developments.

The current National Veld and Forest Fire Act 101 of 1998 does not adequately cater for prescribed burning, as it only allows burning for the purposes of preparing firebreaks. This makes it extremely difficult to obtain permission to conduct fires that would maintain the fynbos, assist with the control of alien plants, and reduce fuel loads.

Another issue is the social resistance to prescribed ecological burns in Cape Town. The public have raised concerns around lack of communication, while the authorities past communications around prescribed and alien clearing has resulted in public efforts to block the planned management actions. This has resulted in a lack of trust between authorities and residents.

These challenges result in a management stalemate.

Recommendations

What should the priorities be in the short-term? Will funds for basic needs, such as recovering buildings and capacity, compete with disaster risk reduction needs, such as ecological restoration and clearing invasive alien trees?

Alien plant management needs to compete with all other budgetary pressures, which perpetuates a complex, wicked problem.

What can be done better going forward?

Firstly, the policy framework needs to be addressed. Although prescribed burns are dangerous and inconvenient, out-of-control wildfires are disastrous and could threaten many people’s lives.

Secondly, citizens of Cape Town need to be more supportive of prescribed ecological burns and alien clearing. The relationship with managing authorities also needs to be restored and trust rebuilt.

Thirdly, Cape Town needs to improve the management of its natural and cultural heritage. This should include both prescribed ecological burns, and keeping the mountain clear of alien trees.

Given the huge interest from the public in alien tree clearing, apparent from the many active volunteer hacking groups, there is a need to integrate efforts by the South African National Parks, the City of Cape Town, and landowners (such as the University of Cape Town) with those of the public to develop a more strategic, standardised approach to clearing invasive alien trees.

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Solar and wind power could break the Grand Ethiopian Renaissance Dam deadlock

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For several years, political tensions between Ethiopia, Sudan and Egypt have been escalating in a conflict over the near-complete Grand Ethiopian Renaissance Dam (GERD). The GERD is Africa’s largest hydropower plant. It dams the Blue Nile river coming from Ethiopia’s highlands just before it crosses into Sudan where, after merging with the White Nile, it continues northwards to Egypt.

Ethiopia needs GERD’s electricity to lift millions of citizens out of poverty. But Egypt is concerned by GERD’s consequences for its agriculture, which depends completely on Nile water. Sudan, meanwhile, sees both potential benefits and risks. Mediation talks to agree on GERD operation have been ongoing for years and are currently stalled.

Why the contention? The GERD’s reservoir will be large enough to store the full annual Blue Nile flow, allowing GERD to produce year-round hydroelectricity. However, such an operational scheme would overhaul the natural timing of the highly seasonal river. Behind many disagreements around GERD hides the question of who, if anyone, should be allowed to exert such control over the Nile.

My colleagues and I have published new research which shows that there are ways out of this controversy and that a win-win situation can be found for GERD’s long-term operation.

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We propose that Ethiopia, Sudan, Egypt and their neighbours deploy large-scale solar and wind farms and establish a regionally integrated power grid. Ethiopia would subsequently need to agree to operate GERD in synergy with solar and wind power.

Although this would entail substantial initial investment, we argue that it would provide tangible benefits to all countries involved and the long-term benefits will outweigh the costs.

GERD and the Nile

Large hydropower plants, like GERD, fill up in the wet season and empty in the dry season, releasing water in a regulated manner throughout the year to ensure year-round electricity generation. This largely suppresses a river’s natural flow.

In GERD’s case, next to ecological concerns surrounding river health, this flow alteration would have implications for the operation of Egypt’s High Aswan Dam (HAD), which Egypt uses to regulate its own Nile flow. Contentious periods may arise in which both dams compete to be filled.

A general view of the Blue Nile river as it passes through the Grand Ethiopian Renaissance Dam in Ethiopia
A general view of the Blue Nile river as it passes through the Grand Ethiopian Renaissance Dam (GERD), near Guba in Ethiopia, on December 26, 2019. EDUARDO SOTERAS/AFP via Getty Images

Aside from this, GERD’s reservoir is large and has Egypt and Sudan worried whether they would receive enough water, especially during dry years. Ethiopia is unwilling to guarantee a fixed amount of downstream releases because it could lead to more general restrictions on the country’s use of the water resources.

Our study shows that the development of alternative electricity sources, to serve as complement to GERD’s hydropower, will automatically address many of these issues.

Alternative energy sources

The key point of our study is that sunshine and wind in many regions of Ethiopia, Sudan and their neighbours have strong seasonalities that are opposite to the seasonal Blue Nile flow. The sun shines brightest and the winds blow strongest during the dry season.

If GERD were operated to back up solar and wind power, this would mean producing less hydropower during the dry season, and more during the wet season, without affecting GERD’s annual average power output. Such an operation would resemble the natural situation.

Reintroduction of seasonality in GERD outflow.

An electricity-based, not water-based, tripartite agreement could be conceived. Ethiopia would have all the benefits expected from a big dam and would not have to make explicit promises on downstream releases. For Sudan and Egypt, it would look as if GERD were a relatively small dam, reassuring them that it does no harm – there are already many such smaller dams on the Nile, which are uncontested. These appear to be the prerequisites for an agreement on GERD.

The proposed solutions will work better if the solar and wind power is deployed on a common, regional grid, such as advocated for by the Eastern African Power Pool – a specialised institution, founded in 2005, to foster power system interconnectivity for East African states.

Investment

Our proposal requires substantial investment shifts towards solar and wind power.

A combined solar and wind power capacity of at least six gigawatt, comparable to GERD’s turbine capacity, will be needed across Ethiopia and its neighbours. Luckily, the region’s resource potential is more than enough for this.

Ethiopia and Sudan are already working on the large-scale deployment of solar and wind parks, which would add up to several hundred megawatt of installed capacity. Egypt appears to have even more ambitious plans for solar and wind power, in the order of several gigawatt.

Getting to the required scale will take years. However, GERD is not yet finished either, with construction works expected to continue until 2023. What’s more, the filling of its reservoir, which started in 2020, is foreseen to take between five and seven years.

Our study shows that the investment needs would be comparable to what GERD has already cost, close to US$5 billion. But this does not mean the plan is financially unattractive.

First, these investments do not need to represent additional costs, but rather reallocations of investments, prioritising solar and wind power before other electricity sources for meeting the region’s ever-rising demand – for which even GERD won’t be enough.

Second, the levelised costs of solar and wind power have fallen so drastically that developing these resources will lead to lower electricity generation costs in Ethiopia, Sudan and Egypt on the long term.

And third, the international community may be keener to support solar and wind development as opposed to new large hydro or fossil fuel plants.

Win-win situations

This hybrid system would be a win-win situation for all, providing various co-benefits aside from unlocking the negotiations and lowering long-term electricity generation costs.

Ethiopia would position itself as a strong electricity exporter in East Africa. And GERD would frequently run at full capacity – during spells of low solar or wind power.

Sudan and Egypt could receive more water during dry years than before because GERD can compensate the interannual variations of Blue Nile flow.

Sudan could substantially displace fossil fuels, and other neighbouring countries could eventually do the same.

Nile river ecology across Sudan would be less affected by GERD since flow seasonality is an important component of rivers’ ecological health.

Egypt would not need to substantially adapt the operation of its own High Aswan Dam (HAD), given the retention of the seasonal character of Blue Nile flow.

Potentially contentious periods, in which GERD fills up while Lake Nasser (Aswan Dam’s reservoir) is still emptying, would be reduced to a minimum.

Integrated hydro-solar-wind planning provides a way forward with common objectives for Ethiopia, Sudan, and Egypt.

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