Catherine Machalaba
Catherine Machalaba
Topic: Ecosystems and health
Catherine Machalaba is the Program Coordinator for Health and Policy at EcoHealth Alliance, a scientific organization working at the intersection of global health, environment and capacity building...
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Number of questions: [6]
Posted on 01/10/2016 09:18:53
i'm glad that i can finally ask a question i've always wanted to ask about ecosystem and health.
Whenever i have chances to talk about ecosystem, there are always people asking me whether there is any beneficial effect of mosquito on our environment or not.
So my question is this.
Do the mosquitos always have a bad impact on us? Then is it fine to eradicate all the mosquitos on earth if it's possible? Is our world going to be a better place without mosquitos?
Considering the health aspects, i would like to hear your opinion about this issue.
Thank you, have a great day!

Chan Jun Park (from Republic of Korea)
Dear Chan Jun Park,

Thank you very much for this question. This is a topic that is being discussed a lot recently, especially in the context of Zika virus. The many intricate links in ecosystems makes this particularly hard to answer. For example, without mosquitos, food availability may be diminished for animals such as insectivorus bats- which provide pollination services that we benefit from for food production and thus nutrition. Even if mosquitos are a relatively small portion of bat diets, many species are increasingly facing a combination of extinction threats, so this could be one more pressure they have to contend with.

There are some fundamental questions that we need to keep in mind when species eradication is proposed. If one species is eradicated, another may assume its niche- with a risk that it could have other or worse detrimental effects on an ecosystem (as seen with invasive species). Feasibility is another – what would it take to eradicate them? In the past, pesticides have been a primary control measure, but vectors have developed resistance in some part of the world– a major challenge for malaria control. The chemical toxicity of pesticides, both to humans and to other species, should also be considered.

It’s also important to consider that anthropogenic activity is often facilitating new risks of vector-borne diseases. For example, the source of West Nile virus introduction into the U.S. in the late 1990’s is thought to be infected mosquitos imported via travel or trade. Partial draining of wetland ecosystems as part of landscape conversion (thereby creating favorable habitats for mosquito breeding and often expanding human populations present in these environments) has been a major problem for malaria transmission in the tropics – and this activity also threatens many other species through habitat destruction.

Given the number of mosquito species in the world (many which don’t bite humans nor transmit pathogens), complete eradication is unlikely; discussions have focused on the ones that are most harmful to humans (primarily those that cause malaria infections). Approaches recently proposed to control Zika virus include genetic engineering to reduce mosquito reproduction or inhibit their transmission of pathogens. Possible trade-offs for ecosystems from synthetic biology remain a big question as we interfere with genetic selection.

While a global question in the context of public health, given the many complex facets of this topic, it warrants consideration on an ecosystem-specific scale to assess possible implications.

In case of interest, some of these and other dimensions are also explored in an insightful news article by the journal Nature ( though please keep in mind that it doesn’t fully delve into environmental risk assessment, both on ecosystem inter-species links and on control measures (e.g. chemical toxicity) components. Thank you again for your question!

Posted on 29/09/2016 08:33:45
Programme ?cosyst?me management a t il possibilit? de nous accompagn?
Coulibaly Modibo (from Mali)
Dear Coulibaly,

Thank you so much for raising this important idea – health is integrally linked to ecosystem management. The IUCN Red List of Ecosystems ( is a useful framework for assessing the health of ecosystems, as measured by the risk of their collapse and degraded or permanent loss of ecosystem services. It was launched recently and hopefully will be expanded to many more sites and be paired with priority actions and implementation of sound management practices. Ecosystem management is a key component of the human-animal-environment interface, helping to address vectorborne, zoonotic, waterborne, and toxicological disease risks, food and water security, agricultural and conservation concerns, and much more. Ecosystem monitoring approaches can be an important part of tracking and refining management strategies, and can provide important sentinel benefits for human health to help detect and address disease threats before they occur.

Posted on 29/09/2016 05:34:51
Hello,,I'm very glad t tel something's for you all,that's about the environmental ,,yes I've natural forest we need to protect but I haven't money to protect it..what should I do??
My email:::
Junol Jaona (from Madagascar)
Dear Junol,

This is a big challenge globally- thank you for raising it. The ecosystem services our forests provide have not been fully valued, especially when considering the many health-benefitting services they are fundamental to (watersheds for water resources, carbon sequestration for climate change mitigation, protection against soil erosion, reducing potential for ecological and exposure conditions for emerging and endemic infectious diseases, and much more). The Intergovernmental Platform on Biodiversity and Ecosystem Services is working to value ecosystem services, but there is still much work to do. Ideally, the value of protecting health-benefitting ecosystem services will be used to strengthen economic valuation of forests through programs like the United Nations Collaborative Programme on Reducing Emissions from Deforestation and Forest Degradation (, which provides incentives for countries to avoid deforestation/forest degradation.

In the meanwhile, we must help inform our policy makers about how health is linked to forests. When considering whether or not to develop forests, the short-term economic benefits are often considered, but we must also calculate the potential health and economic implications for both short and long-term impacts (which may be externalities of development that impact on local communities, such as water security, and may also affect global provisioning of public goods, e.g. as with climate change). One tangible example I like a lot is the economic comparison of New York City’s water source: by protecting the watershed that provides over a billion gallons of water each day, the city avoided the US$6 billion cost of a water treatment facility.

Posted on 28/09/2016 10:18:56
Im looking for conversion factors and standards to measure green house gas emission
Samuel Ndadzibaya (from Zimbabwe)
Dear Samuel,

Thanks for working on this important issue- climate change has many implications for human health, including vector-borne and zoonotic diseases, food and water security, heat stress, natural disasters, and more. We urgently need to work across sectors to reduce greenhouse gas emissions to protect health. Many of the processes linked to the drivers of climate change also contribute to disease burden (as seen with air pollution from burning of fossil fuels). I consulted a leading expert on climate change and health, Professor Andy Haines at the London School of Hygiene and Tropical Medicine and the Future Earth global sustainability research platform, who kindly recommended some resources for your question. The conversion factors would depend on the specific greenhouse gas emissions you refer to – and whether associated with energy, land use, or other, but the Intergovernmental Panel on Climate Change Working Group 1 report should have the information you seek:

The IPCC Working Group 2 has also covered the health effects of climate change, including adaptation and co-benefits of risk mitigation (in public health, the saying is "prevention is better than cure"!):

Kind regards, Catherine

Posted on 27/09/2016 09:05:04
ADD association pour le d?veloppement durablenous solicitons votre apuis intervenir a nos programme que sant? est un vollet tr?s sp?cial
Coulibaly Modibo (from Mali)
Dear Coulibaly,

Sincere thanks for reaching out. Health is a critical component of sustainable development. In addition to Sustainable Development Goal 3 (“Ensure healthy lives and promote well-being for all at all ages”) achievement of other goals (relating to protecting aquatic and terrestrial landscapes, disaster risk reduction, ensuring reliable nutrition sources, and more) may also support health of current and future generations. It is important that synergies be made across the different goals to achieve as much as possible.

I saw your follow-up point as well on health communications. Responses tend to be reactive in responding to both health and environment threats (i.e. once they have already occurred). Messaging is important to keep people aware of the benefits of proactive public health actions to prevent disease before it occurs, especially because prevention is typically vastly less expensive than resource-intensive response/control once a crisis occurs. A 2012 World Bank report estimated a roughly 10:1 return on investment for preventing emerging zoonotic diseases through strengthened veterinary and public health capacity. Media can also also be a superb forum to show how different sectors can play a role in supporting health. I think it’s a wonderful idea to develop health outreach programs via media sources such as radio, television, print, internet and mobile phones. Government authorities can also bring ministries (especially human health, agriculture, and environment, but also colleagues working on disaster risk reduction, land planning, and more) together to promote collaboration for integrated surveillance and control measures. I have some case studies I would be delighted to share if useful.

Merci beaucoup and my apologies for my poor French abilities—hopefully I have understood and addressed your question sufficiently; if not, please do not hesitate to contact me at

Posted on 27/09/2016 05:47:22
Dear Madam,

Which type ecosystem is supported to extreme breeding of mosquitoes in the country like India? And I have heard that mosquitoes have not survived in the country like France? Please elaborate what are the management is required for mosquitoes prevention.
Also tell us is any vaccine has developed by any country or the WHO to fight against vector generation diseases as Dengue, Chicken- guinea etc.

Manoj Kumar Jain
manoj jain (from India)
Dear Manoj,

Many thanks for your question! In fact there isn’t a simple answer – there are over 3,500 known mosquito species, with different suitable habitats (their ecological “niche”) and different preferred hosts for feeding. Not all of these carry pathogens harmful to people (for example, only ~40 species worldwide transmit malaria).

Integrated vector management systems are important for controlling vector-borne diseases. Preventing conditions favorable for their breeding is key, especially removing sources of standing water or treating it with larvicides. The use of bed nets and window screens may also be recommended in some regions with night-biting mosquitos to reduce potential for exposure to mosquito bites. Pesticides are sometimes used in certain regions, seasons with high mosquito activity, and/ or in outbreak situations – but there are many trade-offs that must be considered, including both health and environmental risk assessment given toxicity concerns (an issue in the U.S. in the 1950’s-60’s with the use of DDT for mosquito control after the pesticide entered waterways, was absorbed by aquatic animals, and through the food chain poisoned bald eagles, affecting the egg shells of their offspring and ultimately severely reducing their populations). Protecting ecosystems so we don’t introduce new risk is important (for example by creating conditions where new populations of mosquitos can become established), and some species actually help us with mosquito control- for example, insectivorous bats and birds consume insects, providing an ecosystem service that we can benefit from. The potential effects of environmental changes (e.g. land conversion such as deforestation) on vector ecology and associated health outcomes and their economic implications should be considered when planning development projects.

Vaccines are most certainly in development for these diseases, but are not broadly approved for human use. The CYD-TDV Dengue vaccine was licensed for use in Mexico in late 2015. Some vaccines can help us indirectly; for example, with Rift Valley Fever, a mosquito-borne virus, vaccination of agricultural species susceptible to infection can help break the transmission chain to prevent human cases (a good example of the “One Health” approach that addresses the interface between humans, animals and the environment).

The World Health Organization publishes good information about Dengue control measures, and some of the practices can be applied to address other vector-borne diseases:

Thanks again for your question and concern on this important topic.