Carbon-14 is an important tool in understanding patterns of movement of illegal wildlife products.
Carbon-14 is a naturally occurring isotope produced by cosmic radiation in the upper atmosphere.
Aboveground nuclear weapons testing, primarily in the early 1960s, nearly doubled the concentration of C in the NH was due to higher amounts of testing in the NH compared with the SH.
The rapid decline in elephants across Africa has been attributed to the high poaching rates and increased amount of ivory seized over the last decade or so (3).
Total global seizures in excess of 40 tons of ivory have occurred in several years since 2010 (8), with over 70% of all ivory seizures exceeding 0.5 ton (hereafter termed “large seizures” or “large ivory seizures”).
Zonal heterogeneity in concentrations was observed in each hemisphere in the 1960s and early 1970s and, as a result, multiple calibration curves (e.g., NH1, NH2, and NH3 and SH1–2 and SH3) were established for each hemisphere (10) Global map showing locations of “clean-air” sites used for calibration of the NH zones (NH1, NH2, and NH3) and SH zones (SH1–2 and SH3) for the period from 2000 to 2013; NH3 and SH3 are bounded by the northern and southern limits of the Inter-Tropical Convergence Zone (following ref. ) Remobilization of nonstructural carbon during plant growth: Muhr et al.
(26) have shown that nonstructural carbon in perennial tissues (e.g., branches, stems, and roots) can be mobilized and used for growth several years after fixation and thus F) Time lag between C fixation by plants and ingestion of plants by an elephant: If carbon in the food that animals eat has been fixed previously, there is likely to be an offset of months or years between the date of ingestion and the date of carbon fixation.
For ivory entirely on the rising limb, the innermost dentine should have a higher FC value than the outermost dentine; data from Table S2 show that this is not the case.
For the second case, the outermost dentine would have formed between 19 and the innermost dentine would have formed in the last decade, giving unreasonably slow growth rates for ivory ( All tusks with multiple samples are on the falling limb of the bomb curve, and we thus assume that all other specimens analyzed in this study are on the falling limb.
Central African forest elephant populations decreased by 62% from 2002 to 2011 (5).
Forest elephants are particularly vulnerable to poaching because of their slow population growth rates compared with their savanna counterparts (6).
Modified from Fisher and Fox (32) with permission from University Press of Colorado.