th29 AIM International Workshop

Changes in wood area and CO2 absorption due tourbanization in Tsukuba
Satoko Kawarasaki, NIESAs we move toward renewable energy systems to achieve decarbonization, the carbon dioxide sink function of forests has
become a highly anticipated area of focus. Japanese forests are now reaching maturity and have high absorption capacity, butabsorption is expected to decline in the future. Therefore, it is necessary to increase the amount of carbon sinks.
On the other hand, urban development has led to the clearing of many flat-land, SATOYAMA broad leaved forests for housing
purposes. But even in these areas, vacant land is increasing due to population flow and declining population.
In terms of land use planning, turning vacant land into new sink forests could help build a decarbonized society. In Tsukuba
City, where urbanization has continued over the past few decades, we will conduct a scenario analysis focusing on land use tosee what kind of efforts can be made to transform the city into a decarbonized society in the future.

The present condition and some estimations(Mm3)

Amount of forest biomass inJapan will increase (upper), but
growth will decrease (lower).
Accordingly, CO2 absorbancewill decrease.

(Mm3)

Basic Plan for Forest and Forestry
2021.6(Mha)

Research flow
2030, 2040, 2050, ・・・

Population
density：< n/meshyesLand use：
town
yes

What will be thefuture of Tsukuba?

Compact city(ha)PVJapanese cedar
planted forest

option：1. No use of farmland
2. Use of a part of farmland

afforestation
option：1. Japanese cedar planted forest
2. Broad leaved forest
3. Installing PV (solar paneling)

2015TsukubaIntensiveforestry
Balance between forestry
and agriculture

Ministry of Agriculture, Forestry andFisheries and Tsukuba City

Bothagriculture
and forestry

SATOYAMA
broad leaved
forestoption：n=10, 50, 100, ・・・Japan forest area has notchanged over several decade(upper).
But Tsukuba forest area has
decreased by 20% (lower).

sprawlPopulation distribution•••

Cedar planted forests are high biomass productivity. New cedar planted
forests will aid in future resource supply. If more than 100 km2 of land canbe secured, sustainable forestry operations can be conducted. CO2absorption will be large.
The regeneration of SATOYAMA-broad leaved forests, which used to exist
around cities, will not only provide resources, but also enable biodiversity
conservation. But their productivity will be lower than cedar forests.
PV installation on towns does not burden the natural environment. We
could be self-sufficient in electricity.

Scenario analysis will predict how forest area and biomass accumulation will increase after 2050, how much it will contributeto a decarbonized society as a CO2 sink, and how the society and environment of Tsukuba City will be transformed.
This research is supported by the Environment Research and Technology Development Fund (JPMEERF2325BA006) of the Environmental
Restoration and Conservation Agency provided by Ministry of the Environment of Japan.

2050

Population
density/0.5×
0.5 km2 mesh

Tsukuba
Population density in Ibaraki pref. in 2015 and 2050 (estimation).
There are no changes in high density meshes (>1000), lower density
meshes in 2015 will become smaller in 2050.
National Land Information Division, National Spatial Planning and Regional Policy
Bureau, MLIT of Japan