Can working lands work for conservation? Assessing biodiversity and ecosystem functioning in Chilean timber plantations
Keywords: Biology.

The planet is currently undergoing a period of rapid environmental change, affecting not only individual species, but also the interactions and communities of which they are a part. The disruption of species interactions in turn has far-reaching consequences for ecosystem functioning and human wellbeing. Land use change is a leading driver of biodiversity loss, yet global patterns of land use change have dramatically shifted over the last two decades. Whereas much of the land use literature has focused on the impacts of forest clearing, current land use change is increasingly related to afforestation and the establishment of tree plantations for timber, agriculture, or carbon sequestration. This changing face of land use change offers a new set of challenges and opportunities for biodiversity conservation in working landscapes. Plantations now represent 7% of global land area covered by trees and may provide some habitat for biodiversity where natural forests are scarce. However, they may also replace natural forests and are often criticized as 'biological deserts' that support little biodiversity. In this dissertation, I examine the consequences of tree plantations for biodiversity, with the goal of identifying practical strategies for improving conservation outcomes in plantation landscapes. In my empirical chapters, I use birds as ecological indicators, and I focus on the case of tree plantations in south-central Chile, a global biodiversity hotspot and major timber producing region. Here, tree plantations have dramatically expanded during the last 50 years and prompted widespread concern about their impacts on native biodiversity and ecosystem functioning. After a brief introduction, I begin in Chapter 1 with a literature review of biodiversity in Chilean tree plantations. I found that although plantations can sometimes support substantial biodiversity, there is limited quantitative guidance on how specific management practices mitigate or exacerbate plantation impacts. Attempting to fill this gap, in Chapter 2 I show how landscape tree cover and plantation harvest rates mediate the effects of tree plantations on forest birds. Based on these results, I developed quantitative guidelines for plantation management and assessed current progress towards meeting these criteria in my study area. In doing so, I demonstrate a practical approach for developing ecologically informed, measurable, and verifiable standards to assess plantation contributions to biodiversity conservation goals. In Chapter 3, however, I found that using species occurrence as an indicator of habitat quality may actually underestimate plantation impacts on biodiversity. Although Green-backed Firecrowns frequently occurred in tree plantations, they preferred native forests, which offered more flower resources than plantations, and birds captured in plantations had poorer body condition. This finding supports a growing recognition that static representations of ecological communities often misrepresent the true impacts of environmental change. In response, in Chapter 4, I propose a new conceptual and analytical framework (Predictive Multilayer Networks) for evaluating the multifaceted impacts of environmental change on ecological communities. This framework integrates species interaction networks and spatial networks under a single predictive framework, thereby synthesizing knowledge and techniques from community and landscape ecology and supporting a more holistic understanding of ecological dynamics. The ongoing global expansion of tree plantations represents a major shift in human land use patterns with highly uncertain implications for biodiversity. My research identifies numerous concrete actions that can be taken to reduce plantation impacts. The most important of these is that plantations should not replace native forests. However, there is mounting evidence that protected areas in and of themselves will be unable to reverse the current global biodiversity crisis. Expanding conservation efforts to working lands and other human-dominated landscapes is therefore essential to achieving global biodiversity conservation goals