3.1. Evaluation of supply services
After World War II, in order to quickly restore urban economy, the
process of urbanization has been accelerated. Humans are eager to obtain
materials from the nature and accumulate resources, thus leading to
serious environmental problems such as sharp decline in biodiversity,
river pollution, and green space destruction. Governments and some
scholars of various countries have begun to pay attention to
environmental quality in order to provide sustainable supply resources
for urban development through restoring water bodies and green spaces.
River health evaluation index systems and green space health evaluation
systems have been successively established.
In 1981, based on the concept that a good water ecosystem must have a
perfect biological community structure, with the biological integrity
index (IBI) was first proposed for evaluating the quality of water
environments. After 16 indices of species composition were quantified,
including the indices of nutritional structure and individual health
status, the water environment quality was divided into 6 levels
according to the characteristics of biological integrity (Karr, 1991).
In 1984, the River Invertebrate Prediction and Classification Project
(RIVP-ACS) was proposed (Wright et al. , 1998) to predict the
biomass of macroinvertebrates in a river without any human disturbance
with different characteristics of various areas and then the predicted
biomass value was compared with the actual monitored value of
macroinvertebrates in the river to evaluate the health status of the
river. In 1994, the Australian River Evaluation Program (AUSRIVAS)
(Simpson et al. , 1999) was proposed to predict the theoretical
biomass in a river with the hydrological indices (habitat structure,
water flow state, and continuity), physical and chemical parameters,
indices of invertebrates and fish aggregates, water quality indices, and
ecotoxicological indices.
In general, the evaluation based on these indices can obtain intuitive
results. The obtained biomass reflects the available resource from a
water body, and provides the basis for subsequent fishing or protection.
In these evaluation systems, only the changes in biomass in water
bodies, especially invertebrate biomass, are considered, but whether
invertebrates are index species for the habitat is not considered.
Therefore, these systems cannot accurately reflect the stress on river
ecosystems.
In green space evaluation, the symptoms of land diseases can be
evaluated with key indices such as erosion, fertility loss, hydrological
anomalies, infrequent outbreaks or inexplicable local extinctions of
certain species, and degradation of agricultural products and forestry
products (Carmony, 1992). However, due to the economic development, both
greening construction and environmental protection should be considered
equally. Green coverage rate, green space rate, and park area per capita
should be introduced to the evaluation index system so as to improve
evaluation results (Zhang, 2010). Existing green space evaluation index
systems often only focus on the quantity of green spaces and ignore the
quality of green spaces, so they cannot meet the requirements for
building a high-quality ecological city in the new era. Therefore, in
the future subsequent evaluation system, quantitative and qualitative
indices of water bodies and green spaces should be selected and the
interaction between water bodies and green spaces should be
comprehensively considered to reflect the complex structure and
functions of the blue-green fusion space.