2
Following this introductory chapter, the second chapter covers basic aspects of
physical and ecological science that underlie contemporary scientific understanding
of rivers. This information supports and expands on a primary thesis of the book:
rivers are most appropriately considered as ecosystems rather than as simple channels for downstream conveyance. The intent of the second chapter is to support this
contention by reviewing how physical characteristics of rivers support biotic communities and river ecosystem functions. The third chapter reviews the diversity of
human alterations of rivers throughout history in order to provide context for what
has been changed and why river restoration is so widely undertaken. The final chapter discusses different forms of research and management that are being used to
restore rivers.
First, however, it is useful to consider how different people perceive rivers and
what they mean in using the phrases river health and river ecosystem.
1.1 Perceptions of Rivers
Perceptions and language matter. Consider the jungle versus the rainforest.
Perceptions of the jungle have traditionally been largely negative, emphasizing the
darkness under the dense tree canopy and the danger hidden within that darkness.
This is reflected in expressions such as ‘it’s a jungle out there’ or ‘the urban jungle’.
The word rainforest, which is used for many of the same tropical forest environments as the word jungle, has come to have very positive connotations. Rainforest
is commonly equated with biodiversity and a threatened, fragile environment. A
jungle is something to be overcome and tamed. A rainforest is something to be cherished and protected. I start with this anecdote because human perceptions of natural
environments are at the heart of how we attempt to manage those environments and
whether we emphasize alteration and subjugation of an environment or protection
and restoration. Consequently, the next two sections discuss perceptions of rivers
and river health.
Rivers are one of the most important and endangered ecosystems on Earth. An
ecosystem is a community of living organisms linked together and to the adjacent
environment through fluxes of nutrients and energy. Rivers have sometimes been
conceptualized as simple channels for the downstream conveyance of water and
sediment, but this conceptualization misses the critical aspects of rivers that sustain
life by providing ecosystem services. Ecosystem services include the general categories of provisioning, regulating, supporting, and cultural (MEA 2005), and rivers
provide all of these services abundantly. Provisioning refers to products obtained
from ecosystems. River provisioning comes from water, food such as subsistence
and commercial fisheries, and fertile soil in the floodplain. Regulating describes
benefits obtained from the regulation of ecosystem processes. Regulating in river
ecosystems comes from reduced flood hazards associated with energy dissipation
across floodplains. Supporting ecosystem services are those necessary for the pro1 Introduction
Following this introductory chapter, the second chapter covers basic aspects of
physical and ecological science that underlie contemporary scientific understanding
of rivers. This information supports and expands on a primary thesis of the book:
rivers are most appropriately considered as ecosystems rather than as simple channels for downstream conveyance. The intent of the second chapter is to support this
contention by reviewing how physical characteristics of rivers support biotic communities and river ecosystem functions. The third chapter reviews the diversity of
human alterations of rivers throughout history in order to provide context for what
has been changed and why river restoration is so widely undertaken. The final chapter discusses different forms of research and management that are being used to
restore rivers.
First, however, it is useful to consider how different people perceive rivers and
what they mean in using the phrases river health and river ecosystem.
1.1 Perceptions of Rivers
Perceptions and language matter. Consider the jungle versus the rainforest.
Perceptions of the jungle have traditionally been largely negative, emphasizing the
darkness under the dense tree canopy and the danger hidden within that darkness.
This is reflected in expressions such as ‘it’s a jungle out there’ or ‘the urban jungle’.
The word rainforest, which is used for many of the same tropical forest environments as the word jungle, has come to have very positive connotations. Rainforest
is commonly equated with biodiversity and a threatened, fragile environment. A
jungle is something to be overcome and tamed. A rainforest is something to be cherished and protected. I start with this anecdote because human perceptions of natural
environments are at the heart of how we attempt to manage those environments and
whether we emphasize alteration and subjugation of an environment or protection
and restoration. Consequently, the next two sections discuss perceptions of rivers
and river health.
Rivers are one of the most important and endangered ecosystems on Earth. An
ecosystem is a community of living organisms linked together and to the adjacent
environment through fluxes of nutrients and energy. Rivers have sometimes been
conceptualized as simple channels for the downstream conveyance of water and
sediment, but this conceptualization misses the critical aspects of rivers that sustain
life by providing ecosystem services. Ecosystem services include the general categories of provisioning, regulating, supporting, and cultural (MEA 2005), and rivers
provide all of these services abundantly. Provisioning refers to products obtained
from ecosystems. River provisioning comes from water, food such as subsistence
and commercial fisheries, and fertile soil in the floodplain. Regulating describes
benefits obtained from the regulation of ecosystem processes. Regulating in river
ecosystems comes from reduced flood hazards associated with energy dissipation
across floodplains. Supporting ecosystem services are those necessary for the pro1 Introduction