Insects and Climate Change
When many people think of animals in relation to climate change, endangered species like the polar bear often come to mind. Yet, infact, the vast majority of species affected by climate change are insects.
Due to their cold-blooded nature, insects must live in areas with temperatures that are suitable for their biological processes, for instance development, reproduction and survival. Therefore, climate change will profoundly impact insects, including their physiology (how they live and reproduce), their behaviour and physical features, as well as relationships with other species (like host plants and natural enemies). As a result, immense shifts are predicted in population dynamics, abundance and geographical spread of insects. In turn, these alterations will have positive and negative outcomes for people, livestock and crops, in terms of vulnerability to insect-transmitted diseases, and availability of essential services provided by insects such as pollination and pest regulation.
Research to understand how insects will respond to climate change is still in its infancy, and various gaps exist. For instance, while a variety of bioclimatic models have been developed towards determining likely changes among insect species due to climate change, many such systems focus on broad geographic scales, either continental or global, thereby limiting their translation into practical, local level management options for communities. There is also lack of adequate information on pest biology, outbreak frequencies, ecological, behavioural, physiological and life history responses of insects to climate change, especially in Africa.
In the recent past, icipe has generated significant knowledge with regard to insects and climate change in Africa. A considerable amount of the Centre’s research has been conducted within the Climate Change Impacts on Ecosystem Services and Food Security in Eastern Africa (CHIESA) project implemented by icipe, the Ministry for Foreign Affairs of Finland, and various partners from 2011 – 2015.
Specifically, CHIESA researchers aimed to understand how current and projected climate change scenarios will affect key pests and diseases, as well as beneficial insects, of four important crops: maize, crucifers, avocado and coffee, around Taita Hills (Kenya), Mount Kilimanjaro (Tanzania) and Jimma Highlands (Ethiopia). The pests investigated were maize stemborers (Busseola fusca and Chilo partellus); the diamondback moth (DBM), which damages crucifers; and fruit flies (specifically Bactrocera dorsalis), the false codling moth (Thaumatotibia leucotreta), and thrips, Heliothrips haemorhoidalis, in relation to avocado. The coffee pests studied include the variegated coffee bug, Antestiopsis thunbergii, and the coffee white stemborer, Monochamus leuconotus.
Towards producing microclimatic information specific to the study areas, the researchers used a combination of approaches, including automatic weather stations installed in strategic locations at different altitudes in the three regions, and hundreds of data loggers situated in farmers’ fields. Laboratory studies were conducted to produce life-tables of key pests and natural enemies, and additional factors likely to influence the pest dynamics, such as farming practices and soil factors, were also investigated and correlated with environmental data.
CHIESA researchers established that due to rising temperatures, higher altitude areas will become more suitable for the pests listed above, and as a result their damage on crops will increase significantly. However, the studies showed that although temperature is a major factor, other climatic elements (e.g. rainfall), responses of natural enemies to climate change, soil status and issues related to human activity, for instance environmental degradation, are also playing a role.
Based on these findings, the researchers have provided a range of recommendations to minimise the predicted risks. Suitable natural enemies for the control of stemborers have been identified and are being studied for possible releases in higher altitude areas. Guided by knowledge on their efficacy and tolerance to temperature, natural enemies are being released to control B. dorsalis releases at different altitudes. To sustain pollination efficiency of the honey bee, Apis mellifera, the researchers propose consevation of flowering plants and maintaining of beehives in avocado orchards. Since the efficiency of Cotesia vestalis, a wasp that controls DBM naturally in the lower altitudes is expected to improve in higher altitudes, the wasp can therefore be used in biological control in the latter regions. Wild crucifers provide alternative refuge for DBM in the high altitudes, and they need to be conserved as a way of naturally controlling the pest. To reduce coffee pest and disease impact in present and future climatic conditions, the researchers recommend prevention of deforestation, promotion of tree planting in coffee farms to provide shade, dissemination of existing good coffee agronomic practices, use of risk analysis tools, such as distribution maps and prediction models and biological control of pests and diseases.
The findings of the CHIESA project are currently being validated and disseminated through the Adaptation for Ecosystem Resilience in Africa (AFERIA), a two-year project that commenced in 2016, to be implemented by icipe and the Ministry for Foreign Affairs of Finland and various partners.
Beyond the CHIESA project, icipe has also conducted a variety of studies, for instance to address the growing need for knowledge on the influence and mutualistic interactions between flowering plants and pollinators (including insects) due to climate change. Ongoing analysis of insects and wild fruits around the Taita Hills by the Centre’s Biosystematic Unit, complemented by long term meteorological data obtained through the CHIESA project, is expected to reveal the continued presence or absence of plants, shifts in fruiting periods, insect phenology and the guild of insect species associated with the fruits.
Globally, remote sensing has significantly advanced our understanding of climate systems, including the dynamics and impacts of climate change, by enabling assessments that would not be possible through climate models and conventional observations. The icipe Geoinformatics Unit is using remote sensing to improve generation of pest distribution maps. For instance, using geospatial tools, the researchers have collected data on four key pests of bee diseases in key beekeeping regions of Kenya, resulting in projections of increased honeybee pest risk by 2055 based on current climate and projected climate change scenarios. Although bioclimatic data was most relevant in the results, remote sensing enabled the researchers to incorporate vegetation seasonality variables, thereby improving pest mapping by over 20%. The Unit has also developed a new remote sensing-based methodology to map flowering plants in Africa, and used it to produce the world’s first floral map. Long-term data on flowering patterns in a given landscape helps to understand, among other factors, the climate and ecological stresses that trigger pest and diseases in bee colonies. This information can also be used in evaluating pollination effects and the quantity and quality of beekeeping products.
One of the consequences of climate change is unpredictable weather patterns, leading to severe droughts, as is the case currently in eastern Africa, especially the horn of Africa. This scenario is changing dynamics between insects, people and livestock, especially in the arid and semi-arid regions. For instance, left with no choice, herders are encroaching on wildlife conservancies and protected areas, increasing their chances of coming into contact with disease vectors like tsetse, and contracting zoonotic diseases like trypanosomiasis. As reported elsewhere in this bulletin, research conducted by the icipe Martin Luscher Emerging Infectious Diseases Laboratory showed that in the Shimba Hills National Reserve, one of Kenya’s high biodiversity areas facing considerable human encroachment, has produced breakthrough knowledge on previously unidentified tick-pathogen relationships and a unique tick diversity, which could contribute to morbidity of human and livestock in the region. The Centre continues its research in this area to understand, design strategies and make recommendations to minimise such risks.
icipe is also investigating the connection between climate change induced wildlife declines with population dynamics and biting patterns of mosquitoes. Studies by the Behavioural and Chemical Ecology Unit show that huge losses of wildlife have an impact on risk parameters (e.g abundance and diversity) of mosquitoes. This knowledge is useful in developing predictive models of zoonotic diseases emergence in people.
As the impacts of climate change intensify, research and development partners need to re-assess the performance of existing strategies, for instance in controlling crop pests. In accordance, over the past five years, icipe has developed a climate-smart version of its highly innovative and successful push-pull technology
(http://www.icipe.org/research/plant-health/push-pull-ipm-technology), which addresses the five key constraints of cereal–livestock mixed production systems in Africa – insect pests (stemborers), the parasitic weed Striga (and other weeds), poor soil fertility, soil moisture management, while also fulfilling the need for high quality animal feed. A recent assessment study established that the climate-smart push-pull technology is enabling farmers living in some of the East African regions most severely affected by climate change to stabilise their cereal–livestock mixed production systems, while also increasing yields by 2.5 times, and in addition, integrate dairy farming into their production systems, despite challenges posed by climate of change.
Indeed, this is icipe’s overall goal: to continue to support communities to not only adapt, but to thrive, regardless of the impact of climate change especially in relation to insects. Towards this goal, we intend to continue working with partners to generate knowledge, to enable the design of practical, local level technologies and strategies.