Figure 18.6 depicts the peat subsidence of a plantation on peatlands over time to the
extent the area would be unsuitable for replanting.
Drainability assessments were introduced by RSPO as a requirement prior to
replanting mature oil palm was introduced in the P&C 2013, as measure to prevent
over drainage of peatlands over time and at the same time to encourage the
application of BMPs in order to reduce the subsidence rate of peatlands planted
with oil palm.
The concept of the drainability assessment is to estimate the natural drainage limit
or drainage base (i.e. the point where drainage through gravity flow is no longer
possible) through site measurements and calculations, and calculate the expected
time to reach the drainage base, called “drainage limit time” (DLT) by taking into
consideration the historical subsidence rate of the assessed area. The Drainability
Assessment Procedure (DAP) (RSPO 2019) provides a methodology for determining how the projected future subsidence would affect the relative level of the fields
and the respective drainage outlet from the planation and the ability of water to drain
by gravity in the future. The Procedure requires the drainability assessment to be
conducted 15 years after initial planting (approximately 5 years prior to planned
replanting) of existing plantations on peatland. Phasing out of oil palm is required if
DLT is less than 40 years or 2-crop cycles, whichever higher. That is a safeguard
which lowers the risk of the peatland becoming unproductive and flooded at the
same time leaving behind sufficient layer of peatland for rehabilitation of vegetation
or planting of more water tolerant crop species. Areas which are determined as
having a DLT of 40 years or less may not be replanted with oil palm and must instead
be planted with different crops requiring less drainage (e.g. paludiculture species) or
be rehabilitated back to natural peatland ecosystems.
18.7 Conclusion
The Roundtable on Sustainable Palm Oil (RSPO) has recognized the importance of
addressing the management of oil palm cultivation on peatland. It has recognized
that cultivation of oil palm on peatland can lead to significant environmental impacts
including subsidence, GHG emissions, enhanced fire risk and loss of critical biodiversity. To help reduce the rate of peatland degradation, a key element is Ground
Water Level (GWL) management, followed by proper fertilizer application,
maintaining and enhancing ground surface cover and use of integrated pest management approaches. Over the past 15 years, RSPO has progressively tightened the
restrictions for RSPO members to develop oil palm on peatland (with a ban on new
development on peatland from 2018); it has introduced strict best management
practices (BMPs) for existing oil palm on peatland and, through the Drainability
Assessment Procedure, it has initiated the managed phase out of oil palm on
peatland.
18 Role of the Roundtable on Sustainable Palm Oil (RSPO) in Tropical Peatland. . .
531
extent the area would be unsuitable for replanting.
Drainability assessments were introduced by RSPO as a requirement prior to
replanting mature oil palm was introduced in the P&C 2013, as measure to prevent
over drainage of peatlands over time and at the same time to encourage the
application of BMPs in order to reduce the subsidence rate of peatlands planted
with oil palm.
The concept of the drainability assessment is to estimate the natural drainage limit
or drainage base (i.e. the point where drainage through gravity flow is no longer
possible) through site measurements and calculations, and calculate the expected
time to reach the drainage base, called “drainage limit time” (DLT) by taking into
consideration the historical subsidence rate of the assessed area. The Drainability
Assessment Procedure (DAP) (RSPO 2019) provides a methodology for determining how the projected future subsidence would affect the relative level of the fields
and the respective drainage outlet from the planation and the ability of water to drain
by gravity in the future. The Procedure requires the drainability assessment to be
conducted 15 years after initial planting (approximately 5 years prior to planned
replanting) of existing plantations on peatland. Phasing out of oil palm is required if
DLT is less than 40 years or 2-crop cycles, whichever higher. That is a safeguard
which lowers the risk of the peatland becoming unproductive and flooded at the
same time leaving behind sufficient layer of peatland for rehabilitation of vegetation
or planting of more water tolerant crop species. Areas which are determined as
having a DLT of 40 years or less may not be replanted with oil palm and must instead
be planted with different crops requiring less drainage (e.g. paludiculture species) or
be rehabilitated back to natural peatland ecosystems.
18.7 Conclusion
The Roundtable on Sustainable Palm Oil (RSPO) has recognized the importance of
addressing the management of oil palm cultivation on peatland. It has recognized
that cultivation of oil palm on peatland can lead to significant environmental impacts
including subsidence, GHG emissions, enhanced fire risk and loss of critical biodiversity. To help reduce the rate of peatland degradation, a key element is Ground
Water Level (GWL) management, followed by proper fertilizer application,
maintaining and enhancing ground surface cover and use of integrated pest management approaches. Over the past 15 years, RSPO has progressively tightened the
restrictions for RSPO members to develop oil palm on peatland (with a ban on new
development on peatland from 2018); it has introduced strict best management
practices (BMPs) for existing oil palm on peatland and, through the Drainability
Assessment Procedure, it has initiated the managed phase out of oil palm on
peatland.
18 Role of the Roundtable on Sustainable Palm Oil (RSPO) in Tropical Peatland. . .
531