Legacy Effects

by

L. Allan James

• LAST REVIEWED: 15 January 2015
• LAST MODIFIED: 15 January 2015
• DOI: 10.1093/obo/9780199363445-0019

Introduction

Legacy effects are environmental changes resulting from antecedent human disturbances. The disturbance may be a result of changes in land use and land cover, fire regime, water diversions, introductions of chemicals or isotopes, other disruptions in natural systems, or combinations of these changes. Literally, “legacy” refers to an inherited condition. In the context of modern environmental science, however, “legacy” implies an inheritance from anthropogenically induced change, unless the term is modified. Thus, “legacy effects,” such as legacy pollution, legacy changes to ecosystems or individual species, and legacy sediment, refer to phenomena that resulted from anthropogenic change. On the other hand, a legacy of paleo climate or Holocene sea level rise does not. “Legacy effects” may also be used in reference to subtle or hidden inherited anthropogenic changes to the system. For example, a study comparing two ecological systems in which one is a relatively pristine reference group and the other has been changed by land use may be concerned about unknown legacy effects in the control group. The prevalent implication of “legacy effect” is that changes were moderately large in scale, not brief, recent events of local geographic extent. For example, temporal scales of disturbances are typically decades or longer and spatial scales generally extend to catchments or ecosystems beyond a single site. Legacy effects are important because a full understanding of the dynamics of an environmental system calls for recognition of the long-term history and trajectory of changes. Many hypotheses have been advanced concerning differences in the condition of systems with and without legacy effects. An integrated, process-oriented, historical view of ecological, geomorphic, hydrological, and biogeochemical systems is needed. Where anthropogenic change has been extensive—which is the normal case—the study of legacy effects in conjunction with consideration of ecosystem and landscape sensitivity may reveal important implications of the persistence of impacts that may influence long-term policies for managing global change.

Introductory Works

Vitousek, et al. 1997 recognized a variety of human changes responsible for ecological change. Several conferences and workshops have generated publications as special issues in journals or proceedings volumes that document legacy effects. Luque, et al. 2013 describes ecological effects of a broad array of global environmental changes. Jefferson and Wegmann 2013 introduces a special issue of the journal Anthropocene devoted to anthropogeomorphology. James and Marcus 2006 presents a series of papers on anthropogenic change of river geomorphology. Habersack, et al. 2014 presents a collection of papers addressing the effects of climate change and land use on large river systems. Houben, et al. 2009 covers effects of climate and human activities on sediment budgets in river systems.

• Habersack, H., D. Haspel, and M. Kondolf. 2014. Large rivers in the Anthropocene: Insights and tools for understanding climatic, land use, and reservoir influences. Water Resources Research 50.5: 3641–3646.

  DOI: 10.1002/2013WR014731

  This paper is the preface to a special collection of papers in Water Resources Research. Twelve papers describe changes in hydrology and geomorphology of large rivers caused by climate and land-use changes, including bank erosion, stationarity, uncertainty, water quality, dams, and water extractions with examples from Asia, Europe, and North America.

• Houben, P., H. Wunderlich, and L. Schrott. 2009. Climate and long-term human impact on sediment fluxes in watershed systems. Geomorphology 108.1–2: 1–7.

  DOI: 10.1016/j.geomorph.2008.08.018

  This paper introduces a special issue in the journal Geomorphology focusing on sediment fluxes generated by human activities since the advent of agriculture. The papers were presented at the second open Land Use and Climatic Impacts on Fluvial Systems (LUCIFS) Workshop in Muenzenberg, Germany. LUCIFS was formed under the aegis of International Geosphere—Biosphere Programme, Past Global Changes (IGBP-PAGES).

• James, L. A., and W. A. Marcus. 2006. The human role in changing fluvial systems: Retrospect, inventory and prospect. Geomorphology 79.3–4: 152–171.

  DOI: 10.1016/j.geomorph.2006.06.017

  This paper introduces a special issue on human influences on river systems comprised of papers from the 37th Binghamton Geomorphology Symposium on this topic. It reviews research traditions within geomorphology concerned with human influences and describes each of the papers in the issue.

• Jefferson, A. J., and K. W. Wegmann. 2013, Geomorphology of the Anthropocene: Understanding the surficial legacy of past and present human activities. Anthropocene 2:1–3.

  DOI: 10.1016/j.ancene.2013.10.005

  This editorial presents a series of papers dedicated to human impacts on geomorphic systems, which were presented at the Geological Society of America meeting in Charlotte, NC in 2012. It reviews research traditions within geomorphology concerned with human influences and describes each of the papers in the issue.

• Luque, G. M., M. E. Hochberg, M. Holyoak, et al. 2013. Ecological effects of environmental change. Ecology Letters 16:1–3.

  DOI: 10.1111/ele.12050

  Papers from a 2012 international meeting of ecologists in Paris concerned with biological and ecological effects of global change. Global changes broadly include atmospheric and human alterations as well as invasive species and interacting effects of combinations. The authors call for a greater focus on the role of humans in global ecological change.

• Vitousek, P. M., H. A. Mooney, J. Lubchenco, and J. M. Meilillo. 1997. Human domination of Earth’s ecosystems. Science 277:494–499.

  DOI: 10.1126/science.277.5325.494

  This synthesis presents a conceptual model of human activities as drivers of climate and ecological change. Three primary categories of anthropic change are land transformations, biotic additions and losses, and changes to global biogeochemistry, which drive climate change and loss of biological diversity. Land transformation is the primary driver of loss of global biodiversity.