dc.description.abstract
The idea of Terraformation comes from the science fiction literature,
where humans have the capability of changing a non-habitable planet to
an Earth-like one. Nowadays, Nature is changing rapidly, the poles are
melting, oceans biodiversity is vanishing due to plastic pollution, and the
deserts are advancing at an unstoppable rhythm. This thesis is a first step
towards the exploration of new strategies that could serve to change this
pernicious tendencies jeopardising ecosystems. We suggest it may not
only be possible by adding new species (alien species), but also engineering
autochthonous microbial species that are already adapted to the environment.
Such engineering may improve their functions and capabilities
allowing them to recover the (host) ecosystem upon their re-introduction.
These new functionalities should make the microbes be able to induce a
bottom-up change in the ecosystem: from the micro-scale (microenvironment)
to the macro-scale (even changing the composition of species in the
entire the ecosystem).
To make this possible, the so-called Terraformation strategy needs to
fuse many different fields of knowledge. The focus of this thesis relies
on studying the outcome of the interactions between species and their environment
(Ecology), on making the desired modifications by means of
genetic engineering of the wild-type species (Synthetic Biology), and on
monitoring the evaluation of the current ecosystems’ states, testing the
possible changes, and predicting the future development of possible interventions
(Dynamical Systems).
In order to do so, in this thesis, we have gathered the tools provided by
these different fields of knowledge. The methodology is based on loops
between observation, designing, and prediction. For example, if there is
a lack of humidity in semiarid ecosystems, we then propose to engineer
e.g. Nostoc sp. to enhace its capability to produce extracellular matrix
(increasing water retention). With this framework, we perform a model to
understand the different possible dynamics, by means of dynamical equations to evaluate e.g. when a synthetic strain will remain in the ecosystem
and the effects it will produce. We have also studied spatial models to
predict their ability to modify the spatial organization of vegetation.
Transient dynamics depend on the kind of transition underlying the
occurring tipping point. For this reason, we have studied different systems:
vegetation dynamics with facilitation (typical from drylands), a
cooperator-parasite system, and a trophic chain model where different
human interventions can be tested (i.e. hunting, deforestation, soil degradation,
habitat destruction). All of these systems are shown to promote
different types of transitions (i.e. smooth and catastrophic transitions).
Each transition has its own dynamical fingerprint and thus knowing them
can help monitoring and anticipating these transitions even before they
happen, taking advantage of the so-called early warning signals.
In this travel, we have found that transients can be an important phenomena
in the current changing world. The ecosystems that we observe
can be trapped into a seemingly stable regime, but be indeed in an unstable
situation driving to a future sudden collapse (Fig 1) For this reason,
we need to investigate novel intervention methods able to sustain the current
ecosystems, for instance: Terraformation.
