How Should We Sustain Future Forests Under Extreme Risk?

In this paper we examine the implications of managing for sustained yield in a world characterized by growing risk and uncertainty. We review the history of sustained yield (SY) forestry in North America with its emphasis on economic benefits and the persistence of the SY paradigm today, despite a publicized shift towards managing for a wider range of forest values called Sustainable Forest Management (SFM). We show that current forest management goals around sustainability as well as SFM indicators are still predicated on maximizing harvest levels and timber flows. We build a simple model to explore the implications of SY under extreme (fat-tailed) risk assumptions to show that maximizing a level of harvest without adequately accounting for risk leads towards the depletion of the forest stock with a corresponding decline in the forest economy. We discuss these results in relation to real-world events such as the increase in catastrophic fires and pest outbreaks like the Mountain Pine Beetle in Western Canada. We then examine the theoretical and practical implications that flow from this model and analysis.

Perbandingan Riap Diameter Tegakan Hutan Di Jalur Tanam Dengan Di Jalur Antara Pada Sistem Silvikultur TPTJ

Dalam mengusahakan hutan produksi khususnya yang dikelola dengan sistem silvikultur Tebang Pilih Tanam Jalur (TPTJ) dari suatu unit manajemen, dianut asas kelestarian hasil (sustained yield principle). Apabila besarnya etat volume kayu sama dengan riap, yaitu besarnya volume kayu yang tumbuh pada seluruh tapak dalam waktu satu tahun, maka kelestarian hasil dari suatu unit manajemen akan dapat dicapai. Penelitian ini bertujuan untuk mengetahui perbedaan riap diameter tegakan Dipterocarpaceae pada jalur tanam dengan jalur antara di areal izin konsesi PT Balikpapan Forest Industries di Kabupaten Penajam Paser Utara, Kalimantan Timur Indonesia. Data riap diameter tegakan diperoleh dengan cara mengamati 4 (empat) Petak Ukur Permanen (PUP) dimana masing-masing PUP berukuran 100 m x 100 m. Berdasarkan hasil penelitian diketahui rataan riap diameter tegakan Shorea leprosula di jalur tanam sebesar 2,08 cm/th, sedangkan tegakan jenis komersil pada jalur antara sebesar 1,08 cm/th. Hasil uji statistik dengan uji-t menunjukkan bahwa perbedaan riap diameter antara tegakan Dipterocarpaceae di jalur tanam dengan tegakan jenis komersil di jalur antara tidak menunjukkan perbedaan yang signifikan. Di jalur antara faktor yang menghambat pertumbuhan antara lain : jenis yang beragam, faktor genetik, kerapatan yang tidak teratur, dan persaingan hara. Sedangkan di jalur tanam faktor yang mempercepat pertumbuhan antara lain : intensitas cahaya yang merata, berkurangnya persaingan hara, dan faktor genetik.

A Bayesian life-cycle model to estimate escapement at maximum sustained yield in salmon based on limited information

Life-cycle models combine several strengths for estimating population parameters and biological reference points of harvested species and are particularly useful for those exhibiting distinct habitat shifts and experiencing contrasting environments. Unfortunately, time series data are often limited to counts of adult abundance and harvest. By incorporating data from other populations and by dynamically linking the life-history stages, Bayesian life-cycle models can be used to estimate stage-specific productivities and capacities as well as abundance of breeders that produce maximum sustained yield (MSY). Using coho salmon (Oncorhynchus kisutch) as our case study, we show that incorporating information on marine survival variability from nearby populations can improve model estimates and affect management parameters such as escapement at MSY. We further show that the expected long-term average yield of a fishery managed for a spawner escapement target that produces MSY strongly depends on the average marine survival. Our results illustrate the usefulness of incorporating information from other sources and highlight the importance of accounting for variation in marine survival when making inferences about the management of Pacific salmon.