- reblogged from the future earth blog originally posted Oct 22 2014
Evolutionary biology must be integrated within sustainability science to address pressing global challenges over the long-term.
This piece is co-authored by Scott Carroll.
Evolutionary biology aims to study how and why life changes in composition over time, whether in the genetic makeup of individuals in a population or the diversification of the entire tree of life. Here we focus on two key phenomena, contemporary evolution – the oft-rapid change in the genetic make-up of populations, and phenotype-environment mismatch – the inability of individuals to adapt to their current environment.
Rapid evolution that outstrips human ingenuity, such as antibiotic resistance, and evolution too slow to keep up with environmental change, such as the current extinction crisis, cost society billions or trillions of dollars each year. These costs may deprive humanity of the resources needed to support the shift to sustainable systems of living. The consequences of not accounting for evolution and mismatch are evident in the overwhelming costs of resistance to pesticides, antibiotics and chemotherapies; increases in chronic disease; crop losses to climate extremes; and the less tangible but equally grave ethical and economic costs of biodiversity loss. These challenges worsen as genes are transported (through trade, travel and biophysical processes) in increasing frequency over large distances and between health, production and environmental systems, further underscoring the importance of integrated approaches to sustainable development.
The growing costs of evolution that is either too fast or too slow
Increasing and unquantified costs: The economic, social and ecological costs of rapid evolution and phenotype-environment mismatch are largely unquantified, and we are often left with looking at trends over time. Increases in key trends such as resistance evolution and biodiversity loss are what led biologist Stephen Palumbi to describe “humans as the World’s greatest evolutionary force” in a seminal reviewand book.
Resistance: These trends include the global rise in pathogen resistance to antimicrobial compounds and the increased struggle to deliver replacements. The World Health Organisation (WHO) has repeatedly warned that resistance evolution is one of the largest health challenges facing society. The same trend pervades agriculture, where short-sighted applications of pesticides and the use of genetically modified crops with insecticide genes orherbicide tolerance (such as RoundUp Ready crops) in combination have led to more than 11,000 cases of pesticide resistance evolution spread over more than 1000 species of animal, plant and microbial pests (Tabashnik et al. 2014).
Emerging infectious viral disease: Everybody is talking about it - the costs in number of human lives and the risk of severe economic downturn in a number of West African countries as a consequence of the recent Ebola outbreak. Humans are more likely to contract emerging infectious disease (such as Ebola, SARS, HIV, West Nile Virus etc.) when our intensified land use brings us closer to wildlife populations and with our transport systems that spread their associated pathogens (with associated antimicrobial resistance genes) farther into human populations. Such gene flow can have direct and immediate consequences, as in the recent H1N1 and H5N1 super-flu outbreaks that originated from hybridization of more benign virus strains that human activities brought together. Evolution also contributes to the costs of responding to emerging diseases, as when the HIV virus evolves resistance to antiretroviral drugs.
Costs of phenotype-environment mismatch: The costs to any sustainability trajectory when antibiotics and pesticides lose their efficacy due to rapid evolution are grave enough. Yet the costs of ignoring the slower rate at which humans and many other species evolve likely surpass those burdens by orders of magnitude (think epidemic diseases of civilization: diabetes, heart disease, cancer; think extinction and ecosystem collapse). But how do we quantify the full primary and secondary costs from ruptures in biological systems, declining yields due to altered weather, the loss of unique genetic information through extinction, or human populations affected by chronic disease? It is even meaningful to estimate such numbers? The opportunity cost of failing to develop new crops and pharmaceuticals due to lost wild populations must be large even if intangible (for more information see here and here). Yet many would argue that the most serious cost is the ethical burden of species extinctions. A more tangible burden of phenotype-environment mismatch can be seen in type 2 diabetes mellitus, which largely results from our inability to adapt to modern diets and low physical activity levels, and is estimated to cost around 1 % of world GDP (or 500 billion US dollars) each year.
Are we betting on the right solutions?
Three main strategies: We focused our recent review on progress toward solutions that minimize costs and maximize gains from evolution. An important point to make here is that these solutions are based not only on genetic manipulation, but equally on managing environmental conditions or influencing the development of an organism (such as with vaccines or facilitating learning). Compared to, say, genetic engineering, these commonly involve widely accepted strategies, such as public health policies or protection of natural habitats.
Genetic engineering vs. genetic information: There is much public focus on genetic manipulation, but to date genetic engineering has been successful only within a very narrow scope. For genetically engineered crops, more than 99 % of the grown area (about 10 % of the total global area of crops) contains genes that act as insecticides and/or confer herbicide resistance. We are only now conducting the first experiments with crops engineered to tolerate more general stressors such as droughts or floods. In contrast, traditional breeding strategies augmented with genome sequencing have already produced crops tolerant to weather extremes, such as rice with improved flood tolerance, which now benefits more than one million people in Bangladesh. A similar case can be made with medical gene therapy, which after 25 years of huge investment in development and testing – despite some causes for optimism – has yet to provide successful treatment of a widespread human disease in the United States or Europe. The take-home-message here being that genetic engineering may be very useful, but so far it has been so only with regard to some very specific problems.
Addressing incentive conflicts: Irrespective of the strategy, one of the most dominant barriers to more successful implementation of solutions, as with many other sustainability challenges, is the conflict between individual and group incentives. A textbook example is the conflict between the immediate benefit of antibiotics to an infected person versus the long-term costs to the group of the resistance that may evolve, particularly from incorrect use or over prescription. These incentive conflicts provide a true challenge for regulatory agencies and may be one of the biggest obstacles to the implementation of applied evolutionary biology.
Applied evolutionary biology and sustainability – the road ahead
Convergence: Despite an increasing convergence within applied evolutionary biology, our recent review found little impact of any cross-disciplinary knowledge transfer that may have taken place. There are however several avenues for such cross-fertilization being actively explored:
- Efforts to limit resistance evolution, or other types of undesirable evolution, e.g. in agriculture, infectious disease, cancer biology and harvested marine populations.
- Identification of evolutionary constraints that prevent adaptation to novel environments and lead to chronic diseases in humans and wildlife threatened by habitat change.
- Choices of genetic sources for replanting in forestry, agriculture, environmental restoration and species reintroductions.
The question thus arises as to whether there is need for a forum to facilitate deeper convergence, such as a physical meeting or society.
Sustainability science: The global importance of evolution calls for a stronger integration with sustainability science and its core fields. It is therefore encouraging that many of the key foci of applied evolutionary biology can already be found as foundational concepts of earth system science and the study of socio-ecological systems, two core components of sustainability science. These include system feedback (rapid evolution or the derived consequences of mismatch), coupled systems (gene flow), history-dependent responses (evolutionary constraints), and individual vs. group incentive conflicts (which need to be resolved in the implementation of evolutionarily-informed solutions).
Sustainable development: The current draft sustainable development goals and the Aichi biodiversity targets testify that some progress is being made in integrating applied evolutionary biology into policy frameworks. Progress can especially be found with regard to protecting biodiversity and the genetic diversity of wild crop relatives. More worrying to us is the omission of any reference to resistance or other forms of rapid evolution in the health or food security goals of the sustainable development goals. This is despite new initiatives from WHO, the United States Government and the European Union to address resistance in both sectors at the same time. A unifying policy framework for the use of synthetic biology should be of the highest priority, if we want to reach 2030 in a sustainable manner.
Evolutionary biology has been shown to be a key discipline for addressing some of the most dominant ominous trends within the biological systems on earth. It is becoming increasingly clear that earth system and sustainability science and management that does not take evolutionary perspectives into account may only be successful in the short term, if at all.