Towards benefit oriented rehabilitation to make degraded lakes more resilient to extreme climatic events

ENG- The delineation of the current geological epoch as the “Anthropocene,” derived from the prefix “anthro-” meaning “human,” aptly summarizes the sheer magnitude in which humans have affected the biosphere. For many ecosystems, these pressures have caused long-term degradations to their health and functions. Freshwater systems such as lakes are particularly susceptible as these lentic water bodies act as sentinels of change in the region by accumulating information from the whole catchment. With pressures from anthropogenic actions and climatic scenarios projected to continue, if not intensify, in the coming decades, there is concern regarding the impairment of lake ecosystems. Of the climatic projections, one of the more recent concerns is the intensifying frequency and severity of extreme climatic events (“ECEs”), or a climatic event such as a heatwave or precipitation that is in the tail ends (e.g. 99th percentile) of the distribution curve for that region or time of year. The potential for these events to instigate disproportionate disruptions within freshwater systems worldwide can be significant. Paired with other, non-climatic pressures derived from human actions, such as wide-spread land use change and pandemic outbreaks, there can be multiple pressures affecting the biosphere sequentially or in tandem. Depending upon the nature of the pressure, these can be categorized as “pulse” stressors which are generally short-lived events, such as heatwaves or extreme precipitation, and “press” stressors which have a long-lasting or chronic duration, such as ecosystem alterations (e.g. urbanization, dam construction, etc.) or climate change. Degradation of systems presents challenges not only for the biosphere itself but for human communities as our livelihoods are tied to and built upon the functions and values that the biosphere provides. If the trend of increasing pressures is permitted to continue without intervention, human health, well-being and economies could be impacted just as much as the ecosystem inhabitants. With lakes being the abundantly utilized and vulnerable systems that they are, approaching these multifaceted problems will require looking beyond just the science sector to address present and future challenges. In this thesis, the research traces the cause-effect relationship from 1) the occurrence of extreme event(s) to 2) their implications on ecosystem functions to 3) the effect on ecosystem service provisioning and 4) the implications that intersectoral collaborations could have on ecosystem remediation. This is conducted through an interdisciplinary approach with each chapter using different methodologies to tackle various aspects of this cause-effect chain. Maintaining status quo approaches to utilizing, studying and managing lakes will not be sufficient for improving or preserving ecosystem health and functions in the future. Navigating the razor’s edge of maintained lake functions and services in an extreme world requires informed, proactive, inclusive and holistic methods. By recognizing the urgency of the situation and adapting the approaches used for this new reality, the biosphere and dependent anthropogenic communities may be able to weather the extremes