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Identifying ecosystem services provided by freshwater insects
Published online on 25 August 2015 in Ecological Entomology
Introduction
Biodiversity conservation is increasingly
framed within the ecosystem services
concept. That can result in some taxa
being overlooked, either because their
contribution to ecosystem goods and
services is small, has a non-monetary
value or is unknown. Identifying which
components of biodiversity contribute
the most to ecosystem function and
service delivery is a necessary first step in linking species diversity and ecosystem goods and
services. Consideration of insect-related ecosystem services has largely focussed on terrestrial taxa
while those inhabiting freshwater have been neglected. However, freshwater insects are
fundamental to processes such as decomposition and nutrient cycling.
In Scotland, freshwater ecosystems cover around 2 % of the land area with our lochs and rivers
containing 90% of the UK’s surface freshwater. Freshwater insects can be extremely abundant and
species rich. However, around 25 % of freshwater invertebrate species are under threat of extinction
including several Scottish species such as the Northern summer mayfly (Siphlonurus alternatus). A
decline or loss of specific species and overall species richness is likely to lead to adverse effects on
the delivery of services. For example, loss of species could result in a change in the mean level of
service delivery, or more likely, the resilience of the system to perturbation. To ensure that the
services provided by these insects are available to future generations, we need to ensure that
freshwater insect populations are suitably resilient to threats from pollution, habitat loss and
degradation. The identification of goods and services may bring greater appreciation and impetus to
understanding the scale of their importance, economic value, and conservation.
Key points

The ecosystem services and benefits provided by freshwater insects are diverse and
unexpectedly wide-ranging covering all four categories of services: provisioning, supporting,
regulating and cultural. Several of these have clear economic values but are not currently
fully exploited and there is considerable potential for future development.

Silk sericins produced by caddis flies (Trichoptera) contain proteins which have antioxidant,
moisturising and UV-shielding properties, and are used as additives in cosmetic products.
Many freshwater insects have higher chitin contents than commercially exploited
crustaceans. Chitin is used in the biomedical, pharmaceutical and cosmetic industries.

The breakdown and decomposition of organic matter in freshwater systems is strongly
dependent on specific insect groups and their abundance. Their feeding activities therefore
contribute to nutrient flows and cycling. Burrowing species aerate and rework sediments
further influencing biogeochemical processes.

Contribution to the diets of fish is arguably the most economically important ecosystem
service provided by freshwater insects and around two-thirds of their predators are fish
species. However, they are important prey for a wide range of other invertebrates, reptiles,
amphibians, mammals (e.g. bats) and birds. Freshwater insects also contribute to the
survival of species higher up the food chain. For example, to fish-eating otters.

The adult stages of many freshwater insects, particularly damsel and dragonflies, consume
vast quantities of midges and mosquitoes that are otherwise a nuisance to humans.

Recreational fishing is dependent on freshwater insects to support healthy fish populations.
In Scotland, freshwater fisheries for Salmon and Trout contribute over £112 million annually
to the economy. Aquatic insects like stoneflies and mayflies are an essential source of food
for such fish.

Freshwater insects, particularly dragonflies and mayflies, have inspired and been the subject
of books, paintings, jewellery, films (e.g. Jurassic Park), computer games (e.g. Spyro) and
marketing campaigns (e.g. Vodafone in 2006). They have given their names to shoes, public
houses, aeroplanes, musical outfits, cleaning products, homewares and food and drink
products. The development of micro-helicopters and unmanned aerial vehicles draws
heavily on the mechanics of dragonfly flight.

In the absence of freshwater insects, few other service providers could replicate the same
level and degree of service. The most serious consequences for freshwater habitats would
be a build-up of organic matter or a decline in fish size or populations with repercussions
further up the food chain.
Research undertaken
This briefing is based on a formal review of academic literature and supplemented with grey and
popular literature and resources. The review considered the ecosystem goods and services provided
by freshwater insects globally, though only those relevant to Scotland are included in this briefing.
Economic values were assigned purely on a low, medium or high categorical basis given the
complexity of assigning more precise values to these goods and services. This research was
supported by the Scottish Government’s RESAS Strategic Research Programme 2011-16.
Policy Implications
Although the ecosystem services provided by freshwater insects may not be obvious, they are
fundamental to the provision of clean water and a healthy ecosystem. Few other service providers
could replicate the same level and degree of service. Although the loss of one species may be
compensated by several replacement species or an increase in one specific species, environmental
conditions can, and are, liable to change. Freshwater insects are likely to be particularly vulnerable
to effects of climate change because their dispersal is limited, water temperature and availability are
climate-dependent and they are already subject to many anthropogenic stressors. Thus, preserving a
diversity of species will ensure resilience against unexpected or unwanted circumstances. With a
disproportionate number of species in freshwater habitats compared to terrestrial or marine
habitats, targeted protection of freshwater biodiversity may be critical to meet objectives of
biological diversity conservation.
Freshwater management needs to be applied at the catchment scale. Freshwater sites are
embedded within their watersheds and affected by upstream influences, and freshwater insects are
dependent on a network of connectivity in order to aid migration and dispersal. Furthermore,
threats such as diffuse pollution, sediment and non-native species can only be effectively tackled at
a catchment scale. While freshwater and adjacent riparian habitats in Scotland are generally in good
condition, and have been improved in recent years as a result of Directives such as the Water
Framework Directive and agri-environment schemes, many freshwater insects are still in decline and
pressures are only likely to increase. For example, we need to know what the impacts are of
pesticides and pharmaceutical products on freshwater biota, and how multiple stressors will affect
species persistence and service delivery.
Authors
Craig R. Macadam, Buglife [email protected]
Dr Jenni A. Stockan, James Hutton Institute [email protected]
Topics
Ecosystems and biodiversity
Table 1: Summary of ecosystem goods and services provided by freshwater insects. Adapted from Macadam & Stockan, 2015.
Type of
ecosystem
service
Provisioning
Service or good provided
Silk sericins, chitins
Supporting
Model organisms
Clean water
Regulating
Cultural
Biomass
Clean water
Recreation
Inspiration
Aesthetic appreciation
Taxa involved
Trichoptera (caddis flies), Coleoptera (beetles),
Diptera (flies), Ephemeroptera (mayflies), Odonata
(dragon and damselflies), Plecoptera (stoneflies)
All
Decomposition, nutrient cycling, Diptera, Ephemeroptera, Trichoptera
bioturbation, bioirrigation
Secondary production
All
Bioremediation
Diptera
Recreational fishing
Ephemeroptera, Plecoptera, Trichoptera, (Diptera and
Megaloptera (alderflies) to a lesser extent)
Marketing
Ephemeroptera, Odonata
Education
All
Technology
Ephemeroptera, Odonata
Odonata
Economic value
Low
Low
Medium
Medium
Low
High
Medium
None
Medium
None