Transportation infrastructure – both roads and rail – poses a second and perhaps more serious threat to wildlife trade: Improved transportation networks can facilitate the movement of illegal wildlife traffic. This is an especially serious concern for the CICPEC in Southeast Asia, one of the world’s most active centers for illegal wildlife trafficking (BenYishay et al. 2016; Broussard 2017; Felbab‐Brown 2013a, 2013b). Ultimately, it is this improved transportation efficiency – ironically, a key goal of the BRI Economic Corridors –that presents the greatest threat for some of wildlife species highly prized in East Asian markets. (See Appendix 5: _Illegal logging and wildlife trade in CICPEC_ .)

# II. INDIRECT EFFECTS

Once road and rail projects begin operating, they set into motion additional, unintended changes that can affect the environment even more profoundly than direct effects. Two particularly notable indirect effects are the changes in forest cover and GHG emissions that often result from new frontier access and changes within markets. In this section, we will review the conditions under which the land use and GHG change are most prevalent and the implications for BRI road and rail projects.

## A. Land‐Use Change & Deforestation

Deforestation caused by land‐use changes following changes in transport costs can dramatically exacerbate environmental risks. Road building opens up frontiers to settlement, while increasing market access for farmers and ranchers to forests. Studies of deforestation in Brazil (A. Pfaff et al. 2007), Mexico (G. C. Nelson and Hellerstein 1997), Belize (Chomitz and Gray 1996), and Democratic Republic of Congo (Man Li et al. 2014) indicate some close relationships between road building and deforestation. More − generally, in fact, road building has been correlated with deforestation rates noting that the research has been heavily focused on the impacts within many settings in Latin America in the 1980s and 1990s (Chomitz and Gray 1996; Cropper, Griffiths, and Mani 1999; Deininger and Minten 2002; Ferretti‐Gallon and Busch 2014; Geist and Lambin 2002; G. C. Nelson and Hellerstein 1997; A. S. P. Pfaff 1999). Nearly 95% of all deforestation in the Amazon, occurs within 5.5 km of roads or 1 km of rivers (Barber et al. 2014). This can generate a spiraling loss of forest and increasing damage to biodiversity and ecosystems from forest loss, habitat fragmentation, and edge effects discussed in the Direct Effects section above.

However, spatially‐explicit studies with attention to diverse contexts reveal significant heterogeneity in − the deforestation generated by roads by the locations of roads (and perhaps also the types, although evidence is limited). The degree to which roads lead to deforestation vary with the topography (Freitas, Hawbaker, and Metzger 2010; Hoyos, Cabido, and Cingolani 2018) and agricultural suitability (Ruan, Qiu, and Dyck 2016), local wealth levels (Deininger and Minten 2002; M. Li, Wu, and Deng 2013), protection enforcement (BenYishay et al. 2016; Bhattarai, Conway, and Yousef 2009; Hargrave and Kis‐Katos 2013), and tenure arrangements (Geist and Lambin 2001; Mena, Bilsborrow, and McClain 2006). Crucially for forest dynamics, it has been found that prior land clearing and prior development affect roads’ impacts (Andersen 1996; Cropper, Puri, and Griffiths 2001; A. Pfaff et al. 2018). In sum, for a number of reasons the deforestation that a policy maker should expect due to a new road varies greatly by the setting.

### i. Evidence on Road Impacts Given Prior Development and Deforestation

Chomitz (2007) delineates three main types of forest settings: forest‐agriculture mosaicland where population densities are relatively high, markets are near, and deforestation rate is high for the sparse remaining natural forests; frontier and disputed areas where pressures for deforestation and 12