Introduction
Wetlands are important components of
the natural landscape for their functions in cleaning and retaining
water naturally and providing habitats and food sources for a wide
variety of plant and animal species. As a result of economic development
and human population growth, intensive agriculture (croplands), as well
as changes in water use and availability, increasing urbanisation and
infrastructure development, disease control (especially mosquitoes),
aquaculture, etc., global wetlands continue to convert and degrade.
Historical reports indicate a loss of 87% of the world’s natural
wetland area since the start of the 18th century (Davidson. 2014). What
is more, the natural Wetland Extent Trends index, excluding human-made
wetlands, declined by approximately 30% between 1970 and 2008 globally
(Dixon et al. 2016). Losses of natural inland wetlands have been
consistently greater, and at faster rates, than of natural coastal
wetlands.
The severe loss of wetlands worldwide has significantly increased the
threat to wetland-dependent organisms such as waterfowl (Gregory et al.
2010). For example, China has 65940 km2 of wetlands,
spanning multiple latitudes and accounting for about 10% of the world’s
wetland area, with abundant habitat types, species and quantities of
biological resources. Over the past decade, however, 50% of China’s
bird population density has declined significantly, with inland waters
and marshes experiencing the biggest declines. (Nanjing Institute of
Environmental Sciences, 2018). To counter these negative trends, many
wetland conservation and restoration projects worldwide aim to improve
the wetland biome and increase the diversity of wetland birds (Platteeuw
et al. 2010).
How
to increase wetland biodiversity rapidly is a hot topic in global
discussions. In China, the basic state policy of ecological civilization
construction (the Eighteenth National Congress of the Communist Party of
China, 2012) highlights the pivotal role of wetland ecosystems and their
ecological status for wetland biota. Thus, both protecting existing
wetlands and creating and restoring the functions of degraded wetlands
and their supporting aquatic environments are vital strategic areas for
ecological civilization construction.
For wetland biological management, this importance has led to the goal
of attracting diverse and abundant waterfowl communities from adjacent
habitats. In addition, a variety of foraging habitats and suitable
living conditions (water depth, vegetation, food) can improve the
survival rate of individual birds, as well as the nesting rate and
reproductive success rate of waterbirds in the area. The abundance and
distribution of resources such as fish, plants and macroinvertebrates
are critical to this end (Masero et al. 1999). However, for waterbirds,
access to food resources such as macroinvertebrates and aquatic plants
is constrained by water depth, and the required foraging depths vary
widely among species (Taft et al. 2002; Wood et al. 2012). Additionally,
hydrophytes, depth and substrate affect the abundance and distribution
of macroinvertebrates (Al-Sayed et al. 2008; Di Giovanni et al. 1996).
Consequently, manipulating the water depth and substrate in wetlands can
be a valuable tool that provides habitats for multiple species.
Building artificial ecological islands
(islands for short) is an important
technique for improving wetland topography and providing a diversity of
foraging depths for waterbirds (Burton et al. 1996; Wang et al. 2014).
However, the biodiversity effects of building
these islands have never been
systematically assessed. Furthermore, almost 7 years after these islands
were built, it is still unknown whether this technique for protecting
biodiversity actually protects or promotes biodiversity growth. For
comparative purposes, we therefore surveyed differences in bird and
macroinvertebrate species richness and abundance between sites (Water
with and without islands in the same wetlands). We hypothesized that
when islands are built, there would be differences in the biodiversity
components between sites. Whether biodiversity is affected by islands
was assessed in Fujin National Wetland Park, and the wetland effects
were quantified. From the perspective of restoration ecology, whether
this wetland restoration project of building islands with human
intervention represents a suitable strategy for improving waterfowl and
macroinvertebrate habitats and increasing both their diversity and
abundance were evaluated. This study proposes a technical example of
wetland restoration via a project that provides technical support and a
scientific basis for protecting wetland birds, increasing biodiversity
and protecting and utilizing wetlands on the Sanjiang Plain.