BNPP/ASB Functional Value of Biodiversity Project – Phase II 

1   Introduction

      1.1  Goal and Objectives       

This Implementation Protocol is for Activity 2 of two interrelated sets of activities comprising the second phase of a collaborative research project entitled “Functional Value of Biodiversity (FVOB)”. The general background to the overall project is described in Appendix 1.

The present Activity 2, entitled “Micro/meso Modeling of Hydrological Effects and Cross Scale Effects”, builds on preliminary work on the scale of effects of land cover change on watershed functions in the humid tropics undertaken in Phase I of this project. Phase I review of empirical studies and preliminary simulation results demonstrated (1) the importance of disaggregating the analysis for specific watershed functions (e.g., peak flow, base flow), (2) that this disaggregation could produce results that are more relevant to policymakers’ and public concerns (e.g., flooding, seasonal water shortages), and, not surprisingly, that (3) various modeling strategies have strengths and weaknesses in addressing specific functions.  A team at the University of Washington (UofW) was identified to augment the hydrological modeling capabilities of the lead team from the International Centre for Research in Agroforestry (ICRAF) in Southeast Asia.

In Phase II, the ICRAF Southeast Asia team, which led work in Phase I, the new UofW partners, and other FVOB team members are applying a suite of models with different structures and at different scales to test elements of an emerging consensus among hydrologists that raises fundamental questions about the relationship between hydrological functions and tropical deforestation. This emerging consensus is empirically based, but because of the difficulties and long-term nature of implementing hydrological experiments in the ‘real world’, physically-based simulation provides one important means of testing these propositions within a consistent framework and at multiple scales and thereby helping to explore gaps in evidence.

1.1  Goals 

The goal of this Activity is to use process-based hydrological models to assess the impacts of land cover changes on hydrological effects such as water flow and water quality at the micro (watershed) and meso (river basin) scale. Hence, we will work on nested sites: Mae Chaem – Ping – Chao Phraya – Greater Mekong region on mainland Southeast Asia. See Figure 1 for map of sites.

There are a number of specific objectives in comparing the physical modeling exercises, which are based on real datasets. The researchers hope the models will shed light on the following questions:

1) What is the quantitative impact on the range of ‘watershed function’ indicators of the historical land use change between ‘natural vegetation’ and ‘current land use pattern’?

2) What degradation/recovery can be expected for a number of ‘plausible’ scenarios?

The higher resolution models can also clarify whether landscape patterns (given land use cover data) matter for the functions generated (i.e. is ‘spatial planning’ a relevant part of the answer)? While an initial analysis suggests that ‘segregation’ of forest and agriculture is superior from a biodiversity conservation perspective, and ‘integration’ is better for the maintenance of watershed functions, we will explore the tradeoff over a wide range of population densities. 

One of the hoped for impacts is to help shape the policy agenda on this issue. To the extent feasible, this activity will formulate guidelines or generalizations on the impact of biodiversity-relevant land use changes on hydrological processes such as sedimentation and landslides, as a function of watershed scale, land cover/land use and topography. The policy brief series, outlined in the Appendix, will help set out some guidelines and recommendations for policy makers and decision shapers. The basic ‘policy options’ that exist range from a crude zonation (no agriculture allowed above X m.a.s.l.), via land use zoning on a toposequence, to specific interventions within land use categories (e.g. shade coffee with a litter layer, versus sun coffee with bare soil as in the Sumberjaya site in Sumatra, Indonesia). See Figure 2.

Overall, the system analysis and models will help us to better understand the contributions that land use change, engineering and the location of human activities play in the likelihood of damage. Land use will be analyzed for overall effects (‘deforestation’, land use zoning), effects of spatial landscape organization, as well as for more specific management practices within the major land use classes (litter layers to increase infiltration, sediment filters to reduce overland soil flows) as contributions to integrated solutions. See Figure 3.

Figure 1. Nesting of study watersheds in mainland Southeast Asia.

Figure 3. Human impact of changes in watershed functions are usually due to a combination of  changes in land cover (‘deforestation’), engineering constructions that modify drainage channels and temporary storage structures, and the location where people choose to live. Single-cause attribution of impacts to either of these three categories of causes is likely to be excessively simplistic.

Design and update: Sandra Velarde

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Last updated: 28 November, 2003     ©2003 ASB. All rights reserved.